OFFSET
0,3
LINKS
Colin Barker, Table of n, a(n) for n = 0..1000
Index entries for linear recurrences with constant coefficients, signature (3,-2,-1,0,1,2,-3,1).
FORMULA
Coefficient of x^(n^2) in 1/((1-x)*(1-x^2)*(1-x^3)).
G.f.: (1-2*x+3*x^2+3*x^3+3*x^4+2*x^5+x^6+x^7) / ((1-x)^5*(1+x)*(1+x+x^2)).
a(n) = A001399(n^2) = round((n^2+3)^2/12). - Alois P. Heinz, Jun 16 2016
PROG
(PARI)
\\ b(n) is the coefficient of x^n in the g.f. 1/((1-x)*(1-x^2)*(1-x^3)).
b(n) = round(real((47+9*(-1)^n + 8*exp(-2/3*I*n*Pi) + 8*exp((2*I*n*Pi)/3) + 36*n+6*n^2)/72))
vector(50, n, n--; b(n^2))
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Colin Barker, Jun 16 2016
STATUS
approved