Question

How many five-digit numbers can be formed using the digits 1-9 which have at least three identical digits?

score 2.3k · Answer 1 · 2026-02-23 09:30:43

2.3k

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How many five-digit numbers can be formed using the digits 1-9 which have at least three identical digits?

Published on 23 Feb 2026 - 9:30

score 467 · Answer 2 · 2026-02-23 09:33:46

467

Views

How many natural numbers below 1 million have their sum of digits equal to 18?

Published on 23 Feb 2026 - 9:33

score 158 · Answer 3 · 2026-02-23 09:32:13

158

Views

∀n ∈ N, ∃w1, w2, . . . , wn ∈ A+ such that w = w1w2 . . . wn and C(w) = C(wi) ∀i ∈ {1, . . . , n}

Published on 23 Feb 2026 - 9:32

score 153 · Answer 4 · 2026-02-23 09:30:43

153

Views

Number of non-zero entries of self-convolution

Published on 23 Feb 2026 - 9:30

score 232 · Answer 5 · 2026-02-23 09:33:46

232

Views

Number of non-negative solutions of an equation with restrictions

Published on 23 Feb 2026 - 9:33

score 54 · Answer 6 · 2026-02-23 09:34:28

54

Views

If $A\subset\mathbb{N}$ has A.P.'s of length $k$ for all $k\geq 1,$ then so does $\lceil cA\rceil := \{\lceil ca\rceil:a\in A\}$ for any real $c>0.$

Published on 23 Feb 2026 - 9:34

score 68 · Answer 7 · 2026-02-23 09:32:39

68

Views

Does there exist a maximal subset of arithmetic progressions of length $k,$ such that any additional numbers will result in an A.P. of length $k+2?$

Published on 23 Feb 2026 - 9:32

score 270 · Answer 8 · 2026-02-23 09:27:25

270

Views

Minimum Sum that cannot be obtained from the 1....n with some missing numbers

Published on 23 Feb 2026 - 9:27

score 190 · Answer 9 · 2026-03-27 01:33:06

190

Views

Least Impossible Subset Sum

Published on 27 Mar 2026 - 1:33

score 705 · Answer 10 · 2026-02-23 09:28:49

705

Views

When a set of consecutive numbers can be covered by differences between distinct integers?

Published on 23 Feb 2026 - 9:28

score 107 · Answer 11 · 2026-03-27 13:11:45

107

Views

Convergence of integers by transformations

Published on 27 Mar 2026 - 13:11

score 65 · Answer 12 · 2026-03-27 16:40:37

65

Views

Piecing together full density subsequences

Published on 27 Mar 2026 - 16:40

score 851 · Answer 13 · 2026-03-27 16:15:08

851

Views

A question on Derangement Combinatorics

Published on 27 Mar 2026 - 16:15

score 52 · Answer 14 · 2026-03-26 17:31:55

52

Views

Link between two products

Published on 26 Mar 2026 - 17:31

score 711 · Answer 15 · 2026-02-23 09:32:39

711

Views

Questions on Erdős–Ginzburg–Ziv theorem for primes and understanding related lemmas and their applications.

Published on 23 Feb 2026 - 9:32

List Question

How many five-digit numbers can be formed using the digits 1-9 which have at least three identical digits?

How many natural numbers below 1 million have their sum of digits equal to 18?

∀n ∈ N, ∃w1, w2, . . . , wn ∈ A+ such that w = w1w2 . . . wn and C(w) = C(wi) ∀i ∈ {1, . . . , n}

Number of non-zero entries of self-convolution

Number of non-negative solutions of an equation with restrictions

If $A\subset\mathbb{N}$ has A.P.'s of length $k$ for all $k\geq 1,$ then so does $\lceil cA\rceil := \{\lceil ca\rceil:a\in A\}$ for any real $c>0.$

Does there exist a maximal subset of arithmetic progressions of length $k,$ such that any additional numbers will result in an A.P. of length $k+2?$

Minimum Sum that cannot be obtained from the 1....n with some missing numbers

Least Impossible Subset Sum

When a set of consecutive numbers can be covered by differences between distinct integers?

Convergence of integers by transformations

Piecing together full density subsequences

A question on Derangement Combinatorics

Link between two products

Questions on Erdős–Ginzburg–Ziv theorem for primes and understanding related lemmas and their applications.

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