Question

Counting number of ways a number can be written as the sum of distinct numbers within a certain range

score 2.3k · Answer 1 · 2026-04-12 14:52:31

2.3k

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Counting number of ways a number can be written as the sum of distinct numbers within a certain range

Published on 12 Apr 2026 - 14:52

score 265 · Answer 2 · 2026-04-14 09:11:56

265

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Drawing balls from an urn without replacement: what color runs out first?

Published on 14 Apr 2026 - 9:11

score 102 · Answer 3 · 2026-04-15 07:35:32

102

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Cardinality of $GL_n(Z_{p^{m}})$

Published on 15 Apr 2026 - 7:35

score 626 · Answer 4 · 2026-04-14 15:53:50

626

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How many colors are needed to color an infinite grid so that no sqaure have the same color in all 4 vertexes?

Published on 14 Apr 2026 - 15:53

score 890 · Answer 5 · 2026-03-25 20:36:04

890

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Prove that a graph on $n$ vertices which not contains $K_4$ as a subgraph has at most $\frac{n^2}{3}$ edges.

Published on 25 Mar 2026 - 20:36

score 453 · Answer 6 · 2026-04-16 06:46:57

453

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Number of chords in a $n$-gon if each chord is crossed at most $k$ times

Published on 16 Apr 2026 - 6:46

score 339 · Answer 7 · 2026-04-21 02:35:07

339

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Counting number of words of length $n$

Published on 21 Apr 2026 - 2:35

score 134 · Answer 8 · 2026-04-15 22:16:45

134

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how to understand this theorem of graph theory a crossing number of $C_4 $ x $ C_4$?

Published on 15 Apr 2026 - 22:16

score 147 · Answer 9 · 2026-04-15 14:27:27

147

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How many 5-digit zip codes can exist where the digits are nondecreasing?

Published on 15 Apr 2026 - 14:27

score 572 · Answer 10 · 2026-04-12 14:20:18

572

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Expected value of the number of different objects selected when choosing k objects from n objects with replacement

Published on 12 Apr 2026 - 14:20

score 146 · Answer 11 · 2026-04-12 09:21:10

146

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Choosing subsets of 3 objects out of n, with specific conditions

Published on 12 Apr 2026 - 9:21

score 80 · Answer 12 · 2026-04-21 03:23:11

80

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Using Mobius inversion to determine coefficients.

Published on 21 Apr 2026 - 3:23

score 1.4k · Answer 13 · 2026-04-14 21:44:48

1.4k

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Combinatorics bridge card game.

Published on 14 Apr 2026 - 21:44

score 69 · Answer 14 · 2026-04-03 22:07:21

69

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Is it true that $\sum_{j=k}^{2k} {2k \choose j}\big(\frac{1}{2}\big)^{2k}-\frac{1}{2}=\frac{1}{2}\Big({2k \choose k}\big(\frac{1}{2}\big)^{2k}\Big)$?

Published on 03 Apr 2026 - 22:07

score 426 · Answer 15 · 2026-03-25 04:43:33

426

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There are $n$ different $3$-element subsets $A_1,A_2,...,A_n$ of the set $\{1,2,...,n\}$, with $|A_i \cap A_j| \not= 1$ for all $i \not= j$.

Published on 25 Mar 2026 - 4:43

List Question

Counting number of ways a number can be written as the sum of distinct numbers within a certain range

Drawing balls from an urn without replacement: what color runs out first?

Cardinality of $GL_n(Z_{p^{m}})$

How many colors are needed to color an infinite grid so that no sqaure have the same color in all 4 vertexes?

Prove that a graph on $n$ vertices which not contains $K_4$ as a subgraph has at most $\frac{n^2}{3}$ edges.

Number of chords in a $n$-gon if each chord is crossed at most $k$ times

Counting number of words of length $n$

how to understand this theorem of graph theory a crossing number of $C_4 $ x $ C_4$?

How many 5-digit zip codes can exist where the digits are nondecreasing?

Expected value of the number of different objects selected when choosing k objects from n objects with replacement

Choosing subsets of 3 objects out of n, with specific conditions

Using Mobius inversion to determine coefficients.

Combinatorics bridge card game.

Is it true that $\sum_{j=k}^{2k} {2k \choose j}\big(\frac{1}{2}\big)^{2k}-\frac{1}{2}=\frac{1}{2}\Big({2k \choose k}\big(\frac{1}{2}\big)^{2k}\Big)$?

There are $n$ different $3$-element subsets $A_1,A_2,...,A_n$ of the set $\{1,2,...,n\}$, with $|A_i \cap A_j| \not= 1$ for all $i \not= j$.

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