OFFSET
0,3
LINKS
FORMULA
a(n) = (1/(132*2^n)) * ((55-7*sqrt(33))*(15+3*sqrt(33))^n + (55+7*sqrt(33))*(15-3*sqrt(33))^n).
G.f.: (3*x^2 + 14*x - 1)/(18*x^2 + 15*x - 1).
3^n | a(n+1). - R. J. Mathar, Jan 09 2020
Let b(n)=3^n*A015535(n) = 1,15,243,3915,.. (n>=0). Then 6*a(n) = 5*b(n)-69*b(n-1), n>0. - R. J. Mathar, Aug 19 2022
PROG
(PARI) a(n) = ([1, 2, 3; 4, 5, 6; 7, 8, 9]^n)[1, 1]; \\ Michel Marcus, Oct 26 2018
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Peter James Foreman, Oct 26 2018
STATUS
approved