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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A103212 a(n) = (1/n) * Sum_{i=0..n-1} C(n,i)*C(n,i+1)*(n-1)^i*n^(n-i) for n>=1, a(0)=1.

Original entry on oeis.org

1, 1, 6, 93, 2380, 85405, 3956106, 224939113, 15175702200, 1185580310121, 105302043709390, 10482085765658661, 1156062800841590148, 139945327558704629221, 18449221488652046992914, 2631255715262150125502865, 403689862107153669227378416, 66297391981691913179574751633
Offset: 0

Views

Author

Ralf Stephan, Jan 27 2005

Keywords

Crossrefs

Programs

  • Mathematica
    Table[HypergeometricPFQ[{-n, n+1}, {2}, -n+1], {n, 0, 20}] (* Vaclav Kotesovec, Sep 24 2017 *)
    Flatten[{1, 1, Table[Sum[Binomial[n, k]*Binomial[n, k+1]*(n-1)^k*n^(n-k), {k, 0, n-1}]/n, {n, 2, 20}]}] (* Vaclav Kotesovec, Sep 24 2017 *)
  • PARI
    a(n) = {if(n==0, 1, sum(i=0, n-1, binomial(n,i)*binomial(n,i+1)*(n-1)^i*n^(n-i))/n)} \\ Andrew Howroyd, Apr 14 2021

Formula

a(n) = A103209(n, n-1). [corrected by Vaclav Kotesovec, Sep 24 2017]
a(n) ~ 2^(2*n) * n^(n-3/2) / (sqrt(Pi) * exp(1/2)). - Vaclav Kotesovec, Sep 24 2017

Extensions

Prepended a(0)=1 from Vaclav Kotesovec, Sep 24 2017
Terms a(15) and beyond from Andrew Howroyd, Apr 14 2021

A107702 Triangle related to guillotine partitions of a k-dimensional box by n hyperplanes.

Original entry on oeis.org

1, 1, 1, 1, 2, 1, 1, 3, 6, 1, 1, 4, 15, 22, 1, 1, 5, 28, 93, 90, 1, 1, 6, 45, 244, 645, 394, 1, 1, 7, 66, 505, 2380, 4791, 1806, 1, 1, 8, 91, 906, 6345, 24868, 37275, 8558, 1, 1, 9, 120, 1477, 13926, 85405, 272188, 299865, 41586, 1, 1, 10, 153, 2248, 26845, 229326, 1204245, 3080596, 2474025, 206098, 1
Offset: 0

Views

Author

Paul Barry, May 21 2005

Keywords

Comments

Row sums are A107703. Transpose of square array A103209, read by antidiagonals.

Examples

			Triangle begins:
  1;
  1, 1;
  1, 2,  1;
  1, 3,  6,   1;
  1, 4, 15,  22,    1;
  1, 5, 28,  93,   90,     1;
  1, 6, 45, 244,  645,   394,     1;
  1, 7, 66, 505, 2380,  4791,  1806,    1;
  1, 8, 91, 906, 6345, 24868, 37275, 8558, 1;
  ...
		

Crossrefs

Programs

  • PARI
    T(n, k) = sum(j=0, k, (n-k)^j*binomial(k+j, 2*j)*binomial(2*j, j)/(j+1)); \\ Seiichi Manyama, Oct 02 2023

Formula

Number triangle T(n, k)=if(k<=n, sum{j=0..k, C(k+j, 2j)(n-k)^j*C(j)}, 0), C(n) given by A000108.

A297899 Triangle read by rows, T(n, k) = binomial(n, k)*hypergeom([k-n, n+1], [k+2], -4), for n >= 0 and 0 <= k <= n.

Original entry on oeis.org

1, 5, 1, 45, 10, 1, 505, 115, 15, 1, 6345, 1460, 210, 20, 1, 85405, 19765, 2990, 330, 25, 1, 1204245, 279710, 43635, 5220, 475, 30, 1, 17558705, 4088615, 651165, 81955, 8275, 645, 35, 1, 262577745, 61254760, 9901860, 1290520, 139350, 12280, 840, 40, 1
Offset: 0

Views

Author

Peter Luschny, Jan 08 2018

Keywords

Examples

			Triangle starts:
[0]       1
[1]       5,      1
[2]      45,     10,     1
[3]     505,    115,    15,    1
[4]    6345,   1460,   210,   20,   1
[5]   85405,  19765,  2990,  330,  25,  1
[6] 1204245, 279710, 43635, 5220, 475, 30, 1
		

Crossrefs

T(n, 0) = A133305(n). Row sums are A297705, alternating row sums are A131765.
Cf. A103209.

Programs

  • Mathematica
    T[n_, k_] := Binomial[n, k] Hypergeometric2F1[k - n, n + 1, k + 2, -4];
    Table[T[n, k], {n, 0, 8}, {k, 0, n}] // Flatten
    T[n_, k_] := Sum[4^(j - k)*(k + 1)*Binomial[n + j - k, 2*j - k]*Binomial[2*j - k, j - k]/(j + 1), {j, k, n}];
    Flatten[Table[T[n, k], {n, 0, 8}, {k, 0, n}]] (* Detlef Meya, Jan 15 2024 *)
  • PARI
    T(n,k) = sum(j = k, n, 4^(j - k)*(k + 1)*binomial(n + j - k, 2*j - k)* binomial(2*j - k, j - k)/(j + 1)) \\ Andrew Howroyd, Jan 15 2024

Formula

T(n, k) = Sum_{j = k..n} 4^(j - k)*(k + 1)*binomial(n + j - k, 2*j - k)* binomial(2*j - k, j - k)/(j + 1). - Detlef Meya, Jan 15 2024
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