A294161 Column 1 of triangle A291844.

2, 23, 292, 4068, 62861, 1075562, 20275944, 418724047, 9418874022, 229535650138, 6029910590473, 169978358728536, 5120224516689050, 164192864744507615, 5585978669387706724, 200988595873323113508, 7626780547253339197109, 304431018444668653351250, 12752396616363975496913952, 559388848572350998030227895

Offset

2,1

Links

Gheorghe Coserea, Table of n, a(n) for n = 2..304

Prog

(PARI)
A291843_ser(N, t='t) = {
  my(x='x+O('x^N), y=1, y1=0, n=1,
  dn = 1/(-2*t^2*x^4 - (2*t^2+3*t)*x^3 - (2*t+1)*x^2 + (2*t-1)*x + 1));
  while (n++,
   y1 = (2*x^2*y'*((-t^2 + t)*x + (-t + 1) + (t^2*x^2 + (t^2 + t)*x + t)*y) +
        (t*x^2 + t*x)*y^2 - (2*t^2*x^3 + 3*t*x^2 + (-t + 1)*x - 1))*dn;
   if (y1 == y, break); y = y1; ); y;
};
A291844_ser(N, t='t) = {
  my(z = A291843_ser(N+1, t));
  ((1+x)*z - 1)*(1 + t*x)/((1-t + t*(1+x)*z)*x*z^2);
};
A291844_kol(k, N=20) = {
  my(s = A291844_ser(N+1+3*k\2, t='t + O('t^(k+1))));
  Ser(polcoeff(s, k, 't), 'x, N);
};
Vec(A291844_kol(1))

Crossrefs

Cf. A291844.

Sequence in context: A126040 A354419 A367677 * A088641 A077203 A173935

Adjacent sequences: A294158 A294159 A294160 * A294162 A294163 A294164

Keyword

nonn

Author

Gheorghe Coserea, Nov 04 2017

Status

approved