How can I prove the following identity? $$\large\prod_{k=1}^\infty\frac1{1-2^{1-2k}}=\sum_{m=0}^\infty\left(2^{-\frac{m^2+m}{2}}\prod_{n=1}^\infty\frac{1-2^{-m-n}}{1-2^{-n}}\right)$$ Numerically both sides evaluate to $$2.38423102903137172414989928867839723877...$$
2025-01-13 02:14:26.1736734466
How to prove this infinite product identity?
198 Views Asked by Marty Colos https://math.techqa.club/user/marty-colos/detail At
1
There are 1 best solutions below
Related Questions in CALCULUS
- Derivative of Lambert W function.
- how to use epsilion-delta limit definition to answer the following question?
- Finding the equation of a Normal line
- How to Integrate the Differential Equation for the Pendulum Problem
- Help in finding error in derivative quotient rule
- How to solve the following parabolic pde?
- Finding inflection point
- How to find the absolute maximum of $f(x) = (\sin 2\theta)^2 (1+\cos 2\theta)$ for $0 \le \theta \le \frac{\pi}2$?
- Utility Maximization with a transformed min function
- Interpreting function notation?
Related Questions in SEQUENCES-AND-SERIES
- Series to infinity
- Proving whether the limit of a sequence will always converge to 0?
- How come pi is in this question?
- finding limit equation of a convergent sequence (vn) in math exercise
- Convergence of difference of series
- Proof using triangle inequality
- sum of digits = sum of factors
- My incorrect approach solving this limit. What am I missing?
- Using the Monotone Convergence Theorem to prove convergence of a recursively defined sequence.
- Difference of Riemann sums
Related Questions in INFINITE-PRODUCT
- Generalizations of the pentagonal number theorem
- Find the value of the infinite product $(3)^{\frac{1}{3}} (9)^{\frac{1}{9}} (27)^{\frac{1}{27}}$....
- How do I compute $\prod_{n=1}^\infty \mathrm{e}^{{\mathrm{i}\pi}/{2^n}}$?
- Stuck in proof of Lemma 5.8 in Conway's Functions of one complex variable I
- Find the value of $(1-z)\left(1+\frac{z}{2}\right)\left(1-\frac{z}{3}\right)\left(1+\frac{z}{4}\right)\cdots$.
- First non-zero digit
- Evaluate $A_0=\dfrac{3}{4}$, and $A_{n+1}=\dfrac{1+\sqrt{A_n}}{2}$
- Limit of a sum of infinite series
- What does this product converges to?
- Why is the infinite product of this quotient of $\sin$'s equal to $\left(\frac{3}{\pi}\right)^{2}$[SOLVED]
Related Questions in ARITHMETIC-PROGRESSIONS
- Is it possible that $QR_p = QR_p + x$ for some $p,x$?
- Arithmetic progression. find in terms of n
- Finr the first term and the difference of an arithmetic progression, given two relations between its terms
- In an arithmetic sequence series formula, can n be negative?
- arithmetic progression, finding the nth term.
- Mathematical Induction for $4 + 10 + 16 +…+ (6n−2) = n(3n +1)$
- Define $n$ and $\overline{abcd}$ 4 digit number to satisfy equation
- Primes and arithmetic progressions
- Sequence of sequences
- Which tuple of arithmetic progression sums does the given integer fall into?
Related Questions in GEOMETRIC-PROGRESSIONS
- Induction proof I'm having trouble with: $1+x+x^2+x^3+...+x^n = \frac{1-x^{n+1}}{1-x}$
- Geometrical progression from 1 to $\sqrt5$ to 3 by arithmetics
- Elementary product formula
- Sequence of sequences
- Sum of geometric progression of $(1+x)^{m+n}$
- How to prove this infinite product identity?
- Geometric progression with negative r value
- If $ \sum_{r=1}^{n} t_r $ = $ { n ( n + 1 ) ( n + 2 ) ( n + 3 ) } \over {8} $ , then what does $ \sum_{r=1}^{n} {1\over {t_r} } $ equal to?
- Use geometric progression formula to expand generating function into a power series?
- If $ ax^2 + 2bx + c = 0 $ and $ a_1x^2 + 2b_1x + c_1 = 0 $ have a common root , then prove the following.
Trending Questions
- Induction on the number of equations
- How to convince a math teacher of this simple and obvious fact?
- Refuting the Anti-Cantor Cranks
- Find $E[XY|Y+Z=1 ]$
- Determine the adjoint of $\tilde Q(x)$ for $\tilde Q(x)u:=(Qu)(x)$ where $Q:U→L^2(Ω,ℝ^d$ is a Hilbert-Schmidt operator and $U$ is a Hilbert space
- Why does this innovative method of subtraction from a third grader always work?
- What are the Implications of having VΩ as a model for a theory?
- How do we know that the number $1$ is not equal to the number $-1$?
- Defining a Galois Field based on primitive element versus polynomial?
- Is computer science a branch of mathematics?
- Can't find the relationship between two columns of numbers. Please Help
- Is there a bijection of $\mathbb{R}^n$ with itself such that the forward map is connected but the inverse is not?
- Identification of a quadrilateral as a trapezoid, rectangle, or square
- A community project: prove (or disprove) that $\sum_{n\geq 1}\frac{\sin(2^n)}{n}$ is convergent
- Alternative way of expressing a quantied statement with "Some"
Popular # Hahtags
real-analysis
calculus
linear-algebra
probability
abstract-algebra
integration
sequences-and-series
combinatorics
general-topology
matrices
functional-analysis
complex-analysis
geometry
group-theory
algebra-precalculus
probability-theory
ordinary-differential-equations
limits
analysis
number-theory
measure-theory
elementary-number-theory
statistics
multivariable-calculus
functions
derivatives
discrete-mathematics
differential-geometry
inequality
trigonometry
Popular Questions
- How many squares actually ARE in this picture? Is this a trick question with no right answer?
- What is the difference between independent and mutually exclusive events?
- Visually stunning math concepts which are easy to explain
- taylor series of $\ln(1+x)$?
- Determine if vectors are linearly independent
- What does it mean to have a determinant equal to zero?
- How to find mean and median from histogram
- Difference between "≈", "≃", and "≅"
- Easy way of memorizing values of sine, cosine, and tangent
- How to calculate the intersection of two planes?
- What does "∈" mean?
- If you roll a fair six sided die twice, what's the probability that you get the same number both times?
- Probability of getting exactly 2 heads in 3 coins tossed with order not important?
- Fourier transform for dummies
- Limit of $(1+ x/n)^n$ when $n$ tends to infinity
The identity is in fact true for any $0 < x < 1$: $$\prod_{k=1}^{\infty}\frac{1}{1-x^{2k-1}}=\sum_{m=0}^{\infty}\left(x^{\frac{m^2+m}{2}}\prod_{n=1}^{\infty}\frac{1-x^{m+n}}{1-x^{n}}\right) = \sum_{m=0}^\infty\left(x^{\frac{m^2+m}{2}}\prod_{n=1}^{m}\frac{1}{1-x^{n}}\right)$$
We note the telescopic product: $$\displaystyle \prod_{k=1}^{\infty}\frac{1}{1-x^{2k-1}} = \prod_{k=1}^{\infty} \frac{1-x^{2k}}{1-x^k} = \prod_{k=1}^{\infty}(1+x^k)$$
On the other hand the expression:
\begin{align}\prod_{k=1}^{\infty}(1+x^k) &= \sum_{n=0}^{\infty} \left(\sum\limits_{1\le j_1 < j_2 < \cdots < j_n} x^{j_1+\cdots +j_n}\right)\tag{1}\\&= \sum_{n=0}^{\infty} \left(\sum\limits_{1\le k_1,k_2, \cdots ,k_n} x^{nk_1+(n-1)k_2\cdots +k_n}\right)\tag{2}\\&= \sum_{n=0}^{\infty} \left(\sum\limits_{k_1 \ge 1} x^{nk_1}\sum\limits_{k_2 \ge 1}x^{(n-1)k_2} \cdots \sum\limits_{k_n \ge 1}x^{k_n}\right)\tag{3}\\&= \sum\limits_{n=0}^{\infty} \left(\frac{x^n}{1-x^n}\cdot \frac{x^{n-1}}{1-x^{n-1}}\cdots\frac{x}{1-x}\right)\\&= \sum\limits_{n=0}^{\infty} x^{\frac{n^2+n}{2}}\prod\limits_{m=1}^{n}\frac{1}{1-x^m}\end{align}
Justifications:
$(1)$ Coefficient of $z^n:$ in the infinite product $\displaystyle \prod\limits_{k=1}^{\infty}(1+x^kz)$ being $\displaystyle \left(\sum\limits_{1\le j_1 < j_2 < \cdots < j_n} x^{j_1+\cdots +j_n}\right)$.
$(2)$ Made the change of variable $k_m = j_m - j_{m-1}$ for $m \ge 1$ where, $j_0 = 0$.
Then note that $j_1+\cdots +j_n = nk_1+(n-1)k_{2}+\cdots + k_n$
$(3)$ Used the formula for infinite geometric progression: $\displaystyle \sum\limits_{k\ge 1} x^{mk} = \frac{1}{1-x^m}$