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.

A381773 Expansion of ( (1/x) * Series_Reversion( x/((1+x) * C(x))^3 ) )^(1/3), where C(x) is the g.f. of A000108.

Original entry on oeis.org

1, 2, 15, 157, 1913, 25427, 357546, 5229980, 78765793, 1213181593, 19021747383, 302595975502, 4871780511910, 79232327379407, 1299767617080662, 21481625997258747, 357350097625089497, 5978708468143961925, 100537111802285439375, 1698302173359384479307
Offset: 0

Views

Author

Seiichi Manyama, Mar 07 2025

Keywords

Crossrefs

Programs

  • PARI
    my(N=30, x='x+O('x^N)); Vec((serreverse(x/((1+x)*(1-sqrt(1-4*x))/(2*x))^3)/x)^(1/3))

Formula

G.f. A(x) satisfies A(x) = (1 + x*A(x)^3) * C(x*A(x)^3).
a(n) = Sum_{k=0..n} binomial(3*n+2*k+1,k) * binomial(3*n+1,n-k)/(3*n+2*k+1).

A381787 G.f. A(x) satisfies A(x) = (1 + x) * C(x*A(x)), where C(x) is the g.f. of A000108.

Original entry on oeis.org

1, 2, 5, 22, 112, 623, 3664, 22405, 141002, 907228, 5940663, 39459873, 265228359, 1800608563, 12328843910, 85040632504, 590371016188, 4121775003434, 28921911896836, 203854515625194, 1442669458817907, 10247020573880520, 73024240955785936, 521973882076798493
Offset: 0

Views

Author

Seiichi Manyama, Mar 07 2025

Keywords

Crossrefs

Programs

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

Formula

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

A381832 G.f. A(x) satisfies A(x) = C(x*A(x)^3) / (1 - x), where C(x) is the g.f. of A000108.

Original entry on oeis.org

1, 2, 10, 81, 796, 8616, 98973, 1184324, 14602486, 184219731, 2366543116, 30851212416, 407106050261, 5427274340091, 72986372975716, 988937692146346, 13487903251385562, 185022817888443780, 2551096865411701371, 35335463473311506321, 491444773227779518956, 6860346682881319595632
Offset: 0

Views

Author

Seiichi Manyama, Mar 08 2025

Keywords

Crossrefs

Programs

  • PARI
    a(n) = sum(k=0, n, binomial(5*k+1, k)*binomial(n+2*k, n-k)/(5*k+1));

Formula

a(n) = Sum_{k=0..n} binomial(5*k+1,k) * binomial(n+2*k,n-k)/(5*k+1).
Showing 1-3 of 3 results.