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.

A361835 a(n) = Sum_{k=0..n} (-1)^(n-k) * binomial(2*k,k) * binomial(n*k,n-k).

Original entry on oeis.org

1, 2, 2, -10, -10, 242, -678, -7054, 88342, -207646, -6015904, 88310862, -312514816, -8847633338, 184252541514, -1269592841970, -17662739133178, 634109114537218, -7914500471718552, -18165019012117450, 2936604063787679650, -62899139815867627378
Offset: 0

Views

Author

Seiichi Manyama, Mar 26 2023

Keywords

Crossrefs

Main diagonal of A361834.

Programs

  • PARI
    a(n) = sum(k=0, n, (-1)^(n-k)*binomial(2*k, k)*binomial(n*k, n-k));

Formula

a(n) = [x^n] 1/sqrt(1 - 4*x*(1-x)^n).

A361830 Square array T(n,k), n >= 0, k >= 0, read by antidiagonals downwards, where T(n,k) = Sum_{j=0..n} binomial(2*j,j) * binomial(k*j,n-j).

Original entry on oeis.org

1, 1, 2, 1, 2, 6, 1, 2, 8, 20, 1, 2, 10, 32, 70, 1, 2, 12, 46, 136, 252, 1, 2, 14, 62, 226, 592, 924, 1, 2, 16, 80, 342, 1136, 2624, 3432, 1, 2, 18, 100, 486, 1932, 5810, 11776, 12870, 1, 2, 20, 122, 660, 3030, 11094, 30080, 53344, 48620
Offset: 0

Views

Author

Seiichi Manyama, Mar 26 2023

Keywords

Examples

			Square array begins:
    1,   1,    1,    1,    1,    1, ...
    2,   2,    2,    2,    2,    2, ...
    6,   8,   10,   12,   14,   16, ...
   20,  32,   46,   62,   80,  100, ...
   70, 136,  226,  342,  486,  660, ...
  252, 592, 1136, 1932, 3030, 4482, ...
		

Crossrefs

Columns k=0..5 give A000984, A006139, A137635, A361812, A361813, A361814.
Main diagonal gives A361829.

Programs

  • PARI
    T(n, k) = sum(j=0, n, binomial(2*j, j)*binomial(k*j, n-j));

Formula

G.f. of column k: 1/sqrt(1 - 4*x*(1+x)^k).
n*T(n,k) = 2 * Sum_{j=0..k} binomial(k,j)*(2*n-1-j)*T(n-1-j,k) for n > k.

A361846 a(n) = Sum_{k=0..n} (-9)^k * binomial(-1/3,k) * binomial(n*k,n-k).

Original entry on oeis.org

1, 3, 24, 243, 2973, 41676, 652662, 11228556, 209674050, 4211011422, 90309000630, 2056139084544, 49460437075896, 1251936022103679, 33228751234896060, 922028391785300940, 26676362307801924057, 802875670635086298600
Offset: 0

Views

Author

Seiichi Manyama, Mar 27 2023

Keywords

Crossrefs

Main diagonal of A361839.

Programs

  • PARI
    a(n) = sum(k=0, n, (-9)^k*binomial(-1/3, k)*binomial(n*k, n-k));

Formula

a(n) = [x^n] 1/(1 - 9*x*(1+x)^n)^(1/3).
Showing 1-3 of 3 results.