A055610 A companion sequence to A011896.

0, 0, 0, 1, 2, 5, 9, 15, 24, 36, 52, 71, 95, 123, 156, 195, 240, 292, 350, 416, 489, 570, 660, 759, 868, 986, 1115, 1254, 1404, 1566, 1740, 1927, 2126, 2339, 2565, 2805, 3060, 3330, 3616, 3917, 4235, 4569, 4920, 5289, 5676, 6082, 6506, 6950, 7413, 7896

Offset

0,5

Links

Table of n, a(n) for n=0..49.

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

Formula

G.f.: x^3 * (1 - x + 2*x^2 - x^3 + x^4 + x^5) / ((1 - x)^3 * (1 - x^7)).

a(n) = -A011896(2 - n).

Example

x^3 + 2*x^4 + 5*x^5 + 9*x^6 + 15*x^7 + 24*x^8 + 36*x^9 + 52*x^10 + ...

Prog

(PARI) a(n) = ceil( n * (n-1) * (n-2) / 14)

Crossrefs

Cf. A011896.

Sequence in context: A014126 A019450 A098169 * A134342 A100287 A007176

Adjacent sequences: A055607 A055608 A055609 * A055611 A055612 A055613

Keyword

nonn,easy

Author

Michael Somos, Jun 02 2000

Status

approved