A276130 a(0) = a(1) = a(2) = a(3) = a(4) = 1; for n>4, a(n) = ( a(n-1) +a(n-3) )*( a(n-2)+a(n-4) ) / a(n-5).

1, 1, 1, 1, 1, 4, 10, 55, 649, 38881, 6414706, 24978826228, 2913605221297249, 112139525368095766797655, 8403341152380185679389503620974065, 146904111947501701959735285821948223340424963459227

Offset: 0

Author

Bruno Langlois, Aug 21 2016

Keywords

• nonn

Links

• Seiichi Manyama, Table of n, a(n) for n = 0..22

Crossrefs

Cf. A006721.

Programs

PARI

a(n) = if (n<=4, 1, (9-3*(-1)^n)/2*a(n-1)*a(n-3)-a(n-2)-a(n-4)); \\ Michel Marcus, Aug 27 2016

Formula

a(n) = (9-3*(-1)^n)/2*a(n-1)*a(n-3)-a(n-2)-a(n-4).