Question

How many permutations are of string $1234567$ if digits at index $1\le i \le5$ can't equal the index?

score 521 · Answer 1 · 2026-04-15 07:08:42

521

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How many permutations are of string $1234567$ if digits at index $1\le i \le5$ can't equal the index?

Published on 15 Apr 2026 - 7:08

score 1.9k · Answer 2 · 2026-04-20 04:49:55

1.9k

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Counting the number of bit strings containing a substring

Published on 20 Apr 2026 - 4:49

score 68 · Answer 3 · 2026-04-12 05:06:32

How to find coefficients of a generating function $f$ if we're given the coefficients of the product of $f$ and another generating function?

score 206 · Answer 4 · 2026-04-12 02:57:40

206

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Is $n$ pigeons being unable to occupy $n+1$ holes an alternative formulation of the pigeonhole principle?

Published on 12 Apr 2026 - 2:57

score 1.3k · Answer 5 · 2026-04-12 13:14:26

1.3k

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score 218 · Answer 6 · 2026-04-13 14:24:40

218

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Published on 13 Apr 2026 - 14:24

score 337 · Answer 7 · 2026-04-15 17:50:55

337

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score 244 · Answer 8 · 2026-04-10 13:19:09

244

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score 353 · Answer 9 · 2026-03-25 00:07:42

353

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score 113 · Answer 10 · 2026-04-16 01:20:19

113

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score 90 · Answer 11 · 2026-04-16 08:42:54

Prove that the number of ways of arranging $p$ $1's$ and $q$ $0's$ in a line such that no two $1's$ are adjacent is ${q+1 \choose p}.$

score 1.6k · Answer 12 · 2026-04-11 07:59:45

1.6k

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How to distribute distinct/identical objects into distinct bins if at least some bin must contain more than one object?

Published on 11 Apr 2026 - 7:59

score 263 · Answer 13 · 2026-04-16 14:07:41

263

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Number of permutations of unspecified length

Published on 16 Apr 2026 - 14:07

score 44 · Answer 14 · 2026-04-14 05:31:15

44

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Published on 14 Apr 2026 - 5:31

score 70 · Answer 15 · 2026-04-20 02:40:43

70

Views

Walking positive square numbers and closing or opening doors

Published on 20 Apr 2026 - 2:40

List Question

How many permutations are of string $1234567$ if digits at index $1\le i \le5$ can't equal the index?

Counting the number of bit strings containing a substring

How to find coefficients of a generating function $f$ if we're given the coefficients of the product of $f$ and another generating function?

Is $n$ pigeons being unable to occupy $n+1$ holes an alternative formulation of the pigeonhole principle?

Inclusion-exclusion principle for sets larger than 3

How to prove the case of equality in Schur's inequality?

$16$ rooks on a chess board.

Pigeonhole principle for coprime numbers

confusion in the combinatorial analysis in the game of baccarat

Basic Probability (Deck of Cards)

Prove that the number of ways of arranging $p$ $1's$ and $q$ $0's$ in a line such that no two $1's$ are adjacent is ${q+1 \choose p}.$

How to distribute distinct/identical objects into distinct bins if at least some bin must contain more than one object?

Number of permutations of unspecified length

Is there a probabilistic difference between these two allocating processes?

Walking positive square numbers and closing or opening doors

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