A063026 Reversion of y - y^2 + y^4 - y^5.

0, 1, 1, 2, 4, 9, 21, 52, 135, 368, 1045, 3068, 9230, 28245, 87414, 272544, 854012, 2685897, 8473107, 26805994, 85045674, 270599945, 863529480, 2763745020, 8870777955, 28550721966, 92128996782, 298004209496, 966085311052

Offset: 0

Author

Olivier Gérard, Jul 05 2001

Keywords

• nonn
• easy

Links

• Index entries for reversions of series

Crossrefs

Cf. A063019.

Programs

Mathematica

CoefficientList[InverseSeries[Series[y - y^2 + y^4 - y^5, {y, 0, 30}], x], x]

Formula

a(n+1) = (1/(n+1)) * Sum_{k=0..floor(n/3)} (-1)^k * binomial(n+k,n) * binomial(2*n-3*k,n). - Seiichi Manyama, Sep 26 2023