A152671 Even Catalan numbers divided by 2.

1, 7, 21, 66, 715, 2431, 8398, 29393, 104006, 371450, 1337220, 17678835, 64822395, 238819350, 883631595, 3282060210, 12233133510, 45741281820, 171529806825, 644952073662, 2430973200726, 9183676536076, 34766775458002

Offset

1,2

Links

Table of n, a(n) for n=1..23.

Formula

a(n) = A152670(n)/2.

Mathematica

Select[CatalanNumber[Range[30]], EvenQ]/2 (* Vladimir Reshetnikov, Nov 02 2015 *)

Prog

(PARI) lista(nn) = for (n=1, nn, if (((c=binomial(2*n, n)/(n+1)) % 2) == 0, print1(c/2, ", "))); \\ Michel Marcus, Nov 02 2015

Crossrefs

Cf. A000108, A152670.

Sequence in context: A082541 A005032 A152766 * A113859 A245404 A215494

Adjacent sequences: A152668 A152669 A152670 * A152672 A152673 A152674

Keyword

easy,nonn

Author

Omar E. Pol, Dec 10 2008

Status

approved