OFFSET
0,2
LINKS
FORMULA
G.f.: (1-3*x^2)/(1-3*x-12*x^2) . a(n) = Sum_{k, 0<=k<=n}A122950(n,k)*3^k .
MATHEMATICA
LinearRecurrence[{3, 12}, {1, 3, 18}, 30] (* Harvey P. Dale, Dec 20 2020 *)
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Philippe Deléham, Dec 31 2007
STATUS
approved