A027281 a(n) = Sum_{k=0..2n} (k+1) * A026568(n, k).

1, 6, 21, 76, 235, 738, 2177, 6424, 18423, 52590, 147917, 413796, 1147523, 3166842, 8689305, 23745584, 64621199, 175277574, 473909989, 1277864060, 3436938267, 9223203858, 24699503281, 66020102472, 176160084775, 469293598878

Offset: 0

Author

Clark Kimberling

Keywords

• nonn

Formula

G.f.: (2x^2+4x+1)/(1-x-4x^2)^2.