login
A133594
a(n)=3*a(n-1)+12*a(n-2) for n>=3, a(0)=1, a(1)=3, a(2)=18 .
1
1, 3, 18, 90, 486, 2538, 13446, 70794, 373734, 1970730, 10396998, 54839754, 289283238, 1525926762, 8049179142, 42458658570, 223966125414, 1181402279082, 6231800342214, 32872228375626, 173398289233446, 914661608207850
OFFSET
0,2
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
Sequence in context: A181955 A147518 A088336 * A272492 A092691 A064671
KEYWORD
easy,nonn
AUTHOR
Philippe Deléham, Dec 31 2007
STATUS
approved