cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

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A275063 Number of permutations p of [n] such that p(i)-i is a multiple of eight for all i in [n].

Original entry on oeis.org

1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 4, 8, 16, 32, 64, 128, 256, 768, 2304, 6912, 20736, 62208, 186624, 559872, 1679616, 6718464, 26873856, 107495424, 429981696, 1719926784, 6879707136, 27518828544, 110075314176, 550376570880, 2751882854400, 13759414272000
Offset: 0

Views

Author

Alois P. Heinz, Jul 15 2016

Keywords

Examples

			a(9) = 2: 123456789, 923456781.
		

Crossrefs

Column k=8 of A275062.

Programs

  • Mathematica
    Table[Product[Floor[(n + i)/8]!, {i, 0, 7}], {n, 0, 40}] (* Vaclav Kotesovec, Oct 02 2018 *)

Formula

a(n) = Product_{i=0..7} floor((n+i)/8)!.
a(n) ~ (2*Pi*n)^(7/2) * n! / 8^(n + 4). - Vaclav Kotesovec, Oct 02 2018

A275064 Number of permutations p of [n] such that p(i)-i is a multiple of nine for all i in [n].

Original entry on oeis.org

1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 1536, 4608, 13824, 41472, 124416, 373248, 1119744, 3359232, 10077696, 40310784, 161243136, 644972544, 2579890176, 10319560704, 41278242816, 165112971264, 660451885056, 2641807540224
Offset: 0

Views

Author

Alois P. Heinz, Jul 15 2016

Keywords

Crossrefs

Column k=9 of A275062.

Programs

  • Mathematica
    Table[Product[Floor[(n + i)/9]!, {i, 0, 8}], {n, 0, 40}] (* Vaclav Kotesovec, Oct 02 2018 *)

Formula

a(n) = Product_{i=0..8} floor((n+i)/9)!.
a(n) ~ (2*Pi*n)^4 * n! / 9^(n + 9/2). - Vaclav Kotesovec, Oct 02 2018

A275065 Number of permutations p of [n] such that p(i)-i is a multiple of ten for all i in [n].

Original entry on oeis.org

1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 1024, 3072, 9216, 27648, 82944, 248832, 746496, 2239488, 6718464, 20155392, 60466176, 241864704, 967458816, 3869835264, 15479341056, 61917364224, 247669456896, 990677827584, 3962711310336
Offset: 0

Views

Author

Alois P. Heinz, Jul 15 2016

Keywords

Crossrefs

Column k=10 of A275062.

Programs

  • Maple
    f:= n -> mul(floor((n+i)/10)!,i=0..9):
    map(f, [$0..30]); # Robert Israel, Jul 26 2016
  • Mathematica
    Table[Product[Floor[(n + i)/10]!, {i, 0, 9}], {n, 0, 40}] (* Vaclav Kotesovec, Oct 02 2018 *)

Formula

a(n) = Product_{i=0..9} floor((n+i)/10)!.
a(n) = ((m+1)!)^10/(m+1)^(10-k) where m=floor(n/10)=A059995(n) and k=n mod 10 =A010879(n). - Robert Israel, Jul 26 2016
a(n) ~ (2*Pi*n)^(9/2) * n! / 10^(n + 5). - Vaclav Kotesovec, Oct 02 2018

A335109 Triangle read by rows: T(n,k) is the number of permutations of length n with each cycle of the permutation containing only elements that are identical (mod k), where 1 <= k <= n.

Original entry on oeis.org

1, 2, 1, 6, 2, 1, 24, 4, 2, 1, 120, 12, 4, 2, 1, 720, 36, 8, 4, 2, 1, 5040, 144, 24, 8, 4, 2, 1, 40320, 576, 72, 16, 8, 4, 2, 1, 362880, 2880, 216, 48, 16, 8, 4, 2, 1, 3628800, 14400, 864, 144, 32, 16, 8, 4, 2, 1
Offset: 1

Views

Author

Dennis P. Walsh, May 23 2020

Keywords

Comments

Let [n] denote {1,2,...,n} and let [n](j,k) denote the subset of [n] consisting of all elements of [n] that equal j mod k. The cardinality of [n](j,k) equals ceiling(n/k) for j = 1..(n mod k) and equals floor(n/k) for j > (n mod k). Therefore, upon permuting the elements of each [n](j,k) subset, we obtain T(n,k) = (ceiling(n/k)!)^(n mod k)*(floor(n/k)!)^(k-(n mod k)).

Examples

			Triangle begins:
    1;
    2  1;
    6  2 1;
   24  4 2 1;
  120 12 4 2 1;
  ...
T(6,3) counts the 8 permutations of [6] where all cycle-mates are identical mod 3, namely, (1 4)(2 5)(3 6), (1 4)(2 5)(3)(6), (1 4)(2)(5)(3 6), (1)(4)(2 5)(3 6), (1 4)(2)(5)(3)(6), (1)(4)(2 5)(3)(6), (1)(4)(2)(5)(3 6) and (1)(2)(3)(4)(5)(6).
		

Crossrefs

Programs

  • Maple
    seq(seq((ceil(n/k)!)^(n mod k)*(floor(n/k)!)^(k-(n mod k)), k=1..n), n=1..10);
  • Mathematica
    Table[(Ceiling[n/k]!)^Mod[n, k]*(Floor[n/k]!)^(k - Mod[n, k]), {n, 10}, {k, n}] // Flatten (* Michael De Vlieger, Jun 28 2020 *)

Formula

T(n,k) = (ceiling(n/k)!)^(n mod k)*(floor(n/k)!)^(k-(n mod k)) for 1 <= k <= n.
T(n,1) = A000142(n).
T(n,2) = A010551(n) for n > 1.
T(n,3) = A264557(n) for n > 2.
T(n,4) = A264635(n) for n > 3.
T(n,5) = A264656(n) for n > 4.
T(n,k) = Product_{i=0..k-1} floor((n+i)/k)!. - Alois P. Heinz, May 23 2020
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