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.

Showing 1-3 of 3 results.

A208657 Triangular array read by rows: n*binomial(n,n-k+1)-binomial(n-1,n-k) with k = 1..n, n >= 1.

Original entry on oeis.org

0, 1, 3, 2, 7, 8, 3, 13, 21, 15, 4, 21, 44, 46, 24, 5, 31, 80, 110, 85, 35, 6, 43, 132, 225, 230, 141, 48, 7, 57, 203, 413, 525, 427, 217, 63, 8, 73, 296, 700, 1064, 1078, 728, 316, 80, 9, 91, 414, 1116, 1974, 2394, 2016, 1164, 441, 99, 10, 111, 560, 1695
Offset: 1

Views

Author

Clark Kimberling, Mar 01 2012

Keywords

Comments

Mirror of A208656.

Examples

			Triangle begins:
0,
1, 3,
2, 7, 8,
3, 13, 21, 15,
4, 21, 44, 46, 24,
5, 31, 80, 110, 85, 35,
6, 43, 132, 225, 230, 141, 48,
7, 57, 203, 413, 525, 427, 217, 63,
8, 73, 296, 700, 1064, 1078, 728, 316, 80,
9, 91, 414, 1116, 1974, 2394, 2016, 1164, 441, 99;
...
		

Crossrefs

Cf. A002061 (second column), A208656, A208658 (row sums), A257055.

Programs

  • Magma
    [n*Binomial(n,n-k+1)-Binomial(n-1,n-k): k in [1..n], n in [1..11]]; // Bruno Berselli, Apr 15 2015
  • Mathematica
    z = 12;
    f[n_, k_] := n*Binomial[n, k] - Binomial[n - 1, k - 1]
    t = Table[f[n, k], {n, 1, z}, {k, 1, n}];
    TableForm[t] (* A208656 as a triangle *)
    Flatten[t]   (* A208656 as a sequence *)
    r = Table[f[n, k], {n, 1, z}, {k, n, 1, -1}];
    TableForm[r] (* A208657 as a triangle *)
    Flatten[r]   (* A208657 as a sequence *)
    Table[Sum[f[n, k], {k, 1, n}], {n, 1, 3 z}](* A208658 *)

A208656 Triangle T(n, k) = n*C(n,k) - C(n-1,k-1), 1 <= k <= n, read by rows.

Original entry on oeis.org

0, 3, 1, 8, 7, 2, 15, 21, 13, 3, 24, 46, 44, 21, 4, 35, 85, 110, 80, 31, 5, 48, 141, 230, 225, 132, 43, 6, 63, 217, 427, 525, 413, 203, 57, 7, 80, 316, 728, 1078, 1064, 700, 296, 73, 8, 99, 441, 1164, 2016, 2394, 1974, 1116, 414, 91, 9, 120, 595, 1770
Offset: 1

Views

Author

Clark Kimberling, Mar 01 2012

Keywords

Comments

Mirror of A208657.
col 1: A005563
col 2: A127736
top edge: A000027

Examples

			First five rows:
0
3....1
8....7....2
15...21...13...3
24...46...44...21...4
		

Crossrefs

Programs

  • Mathematica
    z = 12;
    f[n_, k_] := n*Binomial[n, k] - Binomial[n - 1, k - 1]
    t = Table[f[n, k], {n, 1, z}, {k, 1, n}];
    TableForm[t] (* A208656 as a triangle *)
    Flatten[t]   (* A208656 as a sequence *)
    r = Table[f[n, k], {n, 1, z}, {k, n, 1, -1}];
    TableForm[r] (* A208657 as a triangle *)
    Flatten[r]   (* A208657 as a sequence *)
    Table[Sum[f[n, k], {k, 1, n}], {n, 1, 3 z}](* A208658 *)

Extensions

Definition amended by Georg Fischer, Feb 01 2022

A367468 Triangle read by rows: T(n,k) is the total number of movable letters in all members of the k-partitions of [n], with 1 <= k <= n.

Original entry on oeis.org

0, 1, 0, 2, 4, 0, 3, 17, 9, 0, 4, 52, 68, 16, 0, 5, 139, 345, 190, 25, 0, 6, 346, 1474, 1440, 430, 36, 0, 7, 825, 5733, 8904, 4550, 847, 49, 0, 8, 1912, 21048, 49056, 38304, 11928, 1512, 64, 0, 9, 4343, 74385, 251250, 282135, 130998, 27342, 2508, 81, 0
Offset: 1

Views

Author

Stefano Spezia, Nov 19 2023

Keywords

Examples

			Triangle begins:
  0;
  1,   0;
  2,   4,   0;
  3,  17,   9,   0;
  4,  52,  68,  16,  0;
  5, 139, 345, 190, 25, 0;
  ...
		

Crossrefs

Cf. A000290, A008277, A208658, A367469 (row sums).

Programs

  • Mathematica
     T[n_,k_]:=If[k==1,n-1,(2n-1)StirlingS2[n,k]/2-StirlingS2[n+1,k]/2+StirlingS2[n-1,k-2]/2]; Table[T[n,k],{n,10},{k,n}]//Flatten

Formula

T(n,1) = n-1 and T(n,k) = (2*n - 1)*S2(n,k)/2 - S2(n+1,k)/2 + S2(n-1,k-2)/2 for k > 1.
T(n,2) = A208658(n-1).
T(n,n-1) = A000290(n-1) for n > 1.
Showing 1-3 of 3 results.