A139087 G.f. satisfies: 3*A(x) = 5*x + x^2 - 2*Series_Reversion( A(x) ).

1, 1, -4, 50, -892, 19740, -508152, 14692470, -467083420, 16099792940, -595887304312, 23516941477900, -984430022672264, 43531470067595800, -2026833072292353360, 99096914857692255930, -5076210296937439870524

Offset

1,3

Links

Table of n, a(n) for n=1..17.

Formula

a(n) = (2/3)*(-1)^n*A139088(n) for n>2 with a(1)=a(2)=1.

Example

G.f.: A(x) = x + x^2 - 4*x^3 + 50*x^4 - 892*x^5 + 19740*x^6 -+...
Series_Reversion(A(x)) = x - x^2 + 6*x^3 - 75*x^4 + 1338*x^5 -+...
which equals -G(-x) where G(x) = g.f. of A139088.

Prog

(PARI) {a(n)=local(A=x+x^2); if(n<1, 0, for(i=3, n+1, A=A-2*polcoeff(serreverse(A+x*O(x^i)), i)*x^i); polcoeff(A, n))}

Crossrefs

Cf. A139088.

Sequence in context: A123356 A234870 A381753 * A349655 A173218 A380945

Adjacent sequences: A139084 A139085 A139086 * A139088 A139089 A139090

Keyword

sign

Author

Paul D. Hanna, Apr 08 2008

Status

approved