A139088 G.f. satisfies: 2*A(x) = 5*x - x^2 - 3*Series_Reversion( A(x) ).

1, 1, 6, 75, 1338, 29610, 762228, 22038705, 700625130, 24149689410, 893830956468, 35275412216850, 1476645034008396, 65297205101393700, 3040249608438530040, 148645372286538383895, 7614315445406159805786, 407837347813468711863270

Offset

1,3

Links

Table of n, a(n) for n=1..18.

Formula

a(n) = (3/2)*(-1)^n*A139087(n) for n>2 with a(1)=a(2)=1.

Example

G.f.: A(x) = x + x^2 + 6*x^3 + 75*x^4 + 1338*x^5 + 29610*x^6 +...
Series_Reversion(A(x)) = x - x^2 - 4*x^3 - 50*x^4 - 892*x^5 - ...
which equals -G(-x) where G(x) = g.f. of A139087.

Prog

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

Crossrefs

Cf. A139087.

Sequence in context: A049235 A129031 A234529 * A193784 A162863 A216136

Adjacent sequences: A139085 A139086 A139087 * A139089 A139090 A139091

Keyword

nonn

Author

Paul D. Hanna, Apr 08 2008

Status

approved