A112403 G.f.: (1-16*x+28*x^2+56*x^3-140*x^4+56*x^5+28*x^6-16*x^7+x^8)/(x^2-x+1)^8.

1, -8, -72, -120, 330, 1584, 1716, -3432, -12870, -11440, 19448, 63648, 50388, -77520, -232560, -170544, 245157, 692208, 480700, -657800, -1776060, -1184040, 1560780, 4071600, 2629575, -3365856, -8544096, -5379616

Offset

0,2

Comments

Sequence is interesting because the initial terms seem to have many small factors.

Links

Table of n, a(n) for n=0..27.

Formula

a(n) = 2 cos(pi (n+1)/3) binomial(n+7,7). Note that 2 cos(pi (n+1)/3) is always 1, -1, 2, or -2, so this formula explains the small factors. - Dean Hickerson, Feb 06 2006

Crossrefs

Sequence in context: A032554 A097255 A115693 * A043932 A064015 A044576

Adjacent sequences: A112400 A112401 A112402 * A112404 A112405 A112406

Keyword

sign

Author

Creighton Dement, Dec 06 2005

Status

approved