A035318 Right-hand diagonal of A035309.

1, 1, 1, 10, 21, 483, 1485, 56628, 225225, 12317877, 59520825, 4304016990, 24325703325, 2208143028375, 14230536445125, 1564439686929000, 11288163762500625, 1463987089109939625, 11665426077721040625, 1749439028845202483250, 15230046989184655753125

Offset: 0

Author

N. J. A. Sloane

Keywords

• nonn

Links

• Gheorghe Coserea, Table of n, a(n) for n = 0..200

Crossrefs

Cf. A035309.

Programs

Mathematica

a[0] = a[1] = 1;
a[n_] := a[n] = ((4n-2) Mod[n, 2] a[n-1] + (n-1)(2n-3)(2n-1) a[n-2])/(n+1);
Table[a[n], {n, 0, 20}] (* Jean-François Alcover, Aug 30 2019, from PARI *)

PARI

seq(N) = {
  my(a = vector(N)); a[1] = a[2] = 1;
  for (n = 3, N,
       a[n] = ((4*n-2)*(n%2)*a[n-1] + (n-1)*(2*n-3)*(2*n-1)*a[n-2])/(n+1));
  concat(1,a);
};
seq(20)  \\ Gheorghe Coserea, Jan 20 2017

Formula

a(n) = T(n, floor(n/2)), where T(n,g) is defined by A035309. - Gheorghe Coserea, Mar 18 2016

Extensions

More terms from Gheorghe Coserea, Mar 18 2016