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.

A362079 Square array T(n,k), n >= 0, k >= 0, read by antidiagonals downwards, where T(n,k) = [x^n] 1/(1 - x*(1+x)^n)^k.

Original entry on oeis.org

1, 1, 0, 1, 1, 0, 1, 2, 3, 0, 1, 3, 7, 10, 0, 1, 4, 12, 28, 45, 0, 1, 5, 18, 55, 145, 251, 0, 1, 6, 25, 92, 315, 896, 1624, 0, 1, 7, 33, 140, 571, 2106, 6328, 11908, 0, 1, 8, 42, 200, 930, 4076, 15946, 50212, 97545, 0, 1, 9, 52, 273, 1410, 7026, 32718, 134730, 441489, 880660, 0
Offset: 0

Views

Author

Seiichi Manyama, Apr 08 2023

Keywords

Examples

			Square array begins:
  1,   1,   1,    1,    1,    1, ...
  0,   1,   2,    3,    4,    5, ...
  0,   3,   7,   12,   18,   25, ...
  0,  10,  28,   55,   92,  140, ...
  0,  45, 145,  315,  571,  930, ...
  0, 251, 896, 2106, 4076, 7026, ...
		

Crossrefs

Columns k=0..3 give A000007, A099237, A362084, A362085.
Main diagonal gives A362080.
Cf. A362078.

Programs

  • PARI
    T(n, k) = sum(j=0, n, binomial(j+k-1, j)*binomial(n*j, n-j));

Formula

T(n,k) = Sum_{j=0..n} (-1)^j * binomial(-k,j) * binomial(n*j,n-j) = Sum_{j=0..n} binomial(j+k-1,j) * binomial(n*j,n-j).

A362087 a(n) = Sum_{k=0..n} (-1)^k * binomial(-n,k) * binomial(2*k,n-k).

Original entry on oeis.org

1, 1, 7, 37, 215, 1271, 7651, 46614, 286599, 1774630, 11050897, 69134572, 434174819, 2735565574, 17283825370, 109466361512, 694764983463, 4417771590123, 28137563496298, 179478199605550, 1146342590242465, 7330598365285470, 46928753892901140
Offset: 0

Views

Author

Seiichi Manyama, Apr 08 2023

Keywords

Crossrefs

Column k=2 of A362078.
Cf. A362084.

Programs

  • Mathematica
    Table[Sum[Binomial[n + k - 1, k]*Binomial[2*k, n-k], {k, 0, n}], {n, 0, 25}] (* Vaclav Kotesovec, Apr 08 2023 *)
  • PARI
    a(n) = sum(k=0, n, binomial(n+k-1, k)*binomial(2*k, n-k));

Formula

a(n) = Sum_{k=0..n} binomial(n+k-1,k) * binomial(2*k,n-k).
a(n) = [x^n] 1/(1 - x*(1+x)^2)^n.

A362126 Expansion of 1/(1 - x*(1+x)^2)^2.

Original entry on oeis.org

1, 2, 7, 18, 47, 118, 290, 702, 1677, 3966, 9300, 21654, 50116, 115388, 264475, 603792, 1373621, 3115222, 7045205, 15892794, 35769390, 80337144, 180091131, 403002108, 900370600, 2008572044, 4474586920, 9955434456, 22123162421, 49107537598, 108891513251
Offset: 0

Views

Author

Seiichi Manyama, Apr 08 2023

Keywords

Crossrefs

Column k=2 of A362125.

Programs

  • PARI
    my(N=40, x='x+O('x^N)); Vec(1/(1-x*(1+x)^2)^2)

Formula

a(n) = 2*a(n-1) + 3*a(n-2) - 2*a(n-3) - 6*a(n-4) - 4*a(n-5) - a(n-6) for n > 5.
a(n) = Sum_{k=0..n} (-1)^k * binomial(-2,k) * binomial(2*k,n-k) = Sum_{k=0..n} (k+1) * binomial(2*k,n-k).
Showing 1-3 of 3 results.