A390035 a(n) = Sum_{k=0..floor(n/2)} binomial(k+2,3*n-6*k+2).

1, 0, 3, 0, 6, 0, 10, 1, 15, 6, 21, 21, 28, 56, 37, 126, 54, 252, 100, 462, 231, 793, 573, 1299, 1378, 2080, 3108, 3367, 6556, 5733, 13021, 10556, 24583, 20944, 44609, 43453, 78832, 91104, 137808, 188480, 242481, 380190, 436304, 745066, 810381, 1420916, 1553192

Offset

0,3

Links

Seiichi Manyama, Table of n, a(n) for n = 0..1000

Index entries for linear recurrences with constant coefficients, signature (0,3,0,-3,0,1,1).

Formula

G.f.: 1 / ((1-x^2)^3 - x^7).

a(n) = 3*a(n-2) - 3*a(n-4) + a(n-6) + a(n-7).

Prog

(PARI) my(N=50, x='x+O('x^N)); Vec(1/((1-x^2)^3-x^7))

Crossrefs

Cf. A390037.

Sequence in context: A007386 A390222 A007385 * A390219 A392255 A352610

Adjacent sequences: A390032 A390033 A390034 * A390036 A390037 A390038

Keyword

nonn,easy

Author

Seiichi Manyama, Jan 14 2026

Status

approved