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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A349782 Triangle read by rows, T(n, k) = Sum_{j=0..k} |Stirling1(n, j)|.

Original entry on oeis.org

1, 0, 1, 0, 1, 2, 0, 2, 5, 6, 0, 6, 17, 23, 24, 0, 24, 74, 109, 119, 120, 0, 120, 394, 619, 704, 719, 720, 0, 720, 2484, 4108, 4843, 5018, 5039, 5040, 0, 5040, 18108, 31240, 38009, 39969, 40291, 40319, 40320, 0, 40320, 149904, 268028, 335312, 357761, 362297, 362843, 362879, 362880
Offset: 0

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Author

Peter Luschny, Dec 02 2021

Keywords

Comments

T(n, k) is the number of permutations of n objects that contain at most k cycles.

Examples

			Triangle starts:
[0] 1;
[1] 0, 1;
[2] 0, 1,    2;
[3] 0, 2,    5,     6;
[4] 0, 6,    17,    23,    24;
[5] 0, 24,   74,    109,   119,   120;
[6] 0, 120,  394,   619,   704,   719,   720;
[7] 0, 720,  2484,  4108,  4843,  5018,  5039,  5040;
[8] 0, 5040, 18108, 31240, 38009, 39969, 40291, 40319, 40320;
		

Crossrefs

Row sums: A121586, central terms: A349783.

Programs

  • Maple
    T := (n, k) -> add(abs(Stirling1(n,j)), j = 0..k):
    seq(seq(T(n, k), k = 0..n), n = 0..9);
  • Mathematica
    T[n_, k_] := Sum[Abs[StirlingS1[n, j]], {j, 0, k}]; Table[T[n, k], {n, 0, 9}, {k, 0, n}] // Flatten (* Amiram Eldar, Dec 09 2021 *)
  • PARI
    T(n, k) = sum(j=0, k, abs(stirling(n, j, 1))); \\ Michel Marcus, Dec 09 2021

Formula

T(n,k) = Sum_{j=0..k} A132393(n,j). - Alois P. Heinz, Dec 10 2021
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