OFFSET
0,2
LINKS
Colin Barker, Table of n, a(n) for n = 0..650
FORMULA
Coefficient of x^(3^n) in 1/((1-x)*(1-x^2)*(1-x^3)*(1-x^4)).
Conjectures (Start)
a(n) = ((3+3^n)^2*(9+3^n))/144 for n>1.
a(n) = 40*a(n-1)-390*a(n-2)+1080*a(n-3)-729*a(n-4) for n>4.
G.f.: (1-37*x+288*x^2-405*x^3-81*x^4) / ((1-x)*(1-3*x)*(1-9*x)*(1-27*x)).
(End)
PROG
(PARI)
\\ b(n) is the coefficient of x^n in the g.f. 1/((1-x)*(1-x^2)*(1-x^3)*(1-x^4)).
b(n) = round(real(68+36*(-1)^n+18*((-I)^n+I^n)+(16*exp(-2/3*I*n*Pi)*(1+I*sqrt(3)+2*exp((4*I*n*Pi)/3)))/(1+(-1)^(1/3))+59*(1+n)+9*(-1)^n*(1+n)+18*(1+n)*(2+n)+2*(1+n)*(2+n)*(3+n))/288)
vector(20, n, n--; b(3^n))
CROSSREFS
KEYWORD
nonn
AUTHOR
Colin Barker, Jun 17 2016
STATUS
approved