A287031 Column 1 of A286782.

3, 45, 637, 9567, 156123, 2781389, 54043365, 1141864959, 26137086451, 645573913005, 17138071687053, 487130581207775, 14771502665168715, 476244289169954253, 16274079501768450421, 587711952558035789055, 22370368544174736836835, 895269564785985107345453, 37585737112233443277746589

Offset: 2

Author

Gheorghe Coserea, May 18 2017

Keywords

• nonn

Links

• Gheorghe Coserea, Table of n, a(n) for n = 2..211

Crossrefs

Cf. A286782.

Programs

PARI

A286781_ser(N, t='t) = {
  my(x='x+O('x^N), y0=1+O('x^N), y1=0, n=1);
  while(n++,
    y1 = (1 + x*y0 + 2*x^2*y0')*(1 - x*y0*(1-t))/(1-x*y0)^2;
    if (y1 == y0, break()); y0 = y1; );
  y0;
};
A286782_ser(N, t='t) = my(s=A286781_ser(N, t)); 1 + x*s + 2*x^2 * deriv(s,'x);
Kol(K, N=20) = {
  my(v = A286782_ser(N+K+1, 't+O('t^(K+1))));
  vector(N, n, polcoeff(polcoeff(v, K+n), K));
};
Kol(1)

Formula

a(n) = (2*n-1)*A286786(n-1).