A139085 G.f. satisfies: 2*A(x) = 3*x + x^2 - Series_Reversion( A(x) ).

1, 1, -2, 15, -158, 2058, -31148, 529209, -9882430, 200035242, -4346788764, 100697241762, -2473869382964, 64191822293220, -1753530264442280, 50293662225989739, -1511101241900117982, 47467602491174747046

Offset

1,3

Links

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

Formula

a(n) = (1/2)*(-1)^n*A139086(n) for n>2 with a(1)=a(2)=1.

Example

G.f.: A(x) = x + x^2 - 2*x^3 + 15*x^4 - 158*x^5 + 2058*x^6 -+...
Series_Reversion(A(x)) = x - x^2 + 4*x^3 - 30*x^4 + 316*x^5 -+...
which equals -G(-x) where G(x) = g.f. of A139086.

Prog

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

Crossrefs

Cf. A139086.

Sequence in context: A239107 A124548 A324463 * A268070 A204679 A363564

Adjacent sequences: A139082 A139083 A139084 * A139086 A139087 A139088

Keyword

sign

Author

Paul D. Hanna, Apr 08 2008

Status

approved