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A015487
a(0)=1, a(1)=3, a(n) = sum_{k=0}^{k=n-1} 3^k a(k).
0
1, 3, 10, 100, 2800, 229600, 56022400, 40896352000, 89481218176000, 587175753670912000, 11557967535258231808000, 682497982956998588262400000, 120903152684866385913507635200000
OFFSET
0,2
FORMULA
a(n) = (3^(n-2) + 1) * a(n-1). - Vincenzo Librandi, Nov 10 2012
PROG
(Magma) I:=[1, 3, 10]; [n le 3 select I[n] else (3^(n-2)+1)*Self(n-1): n in [1..15]]; // Vincenzo Librandi, Nov 10 2012
CROSSREFS
Sequence in context: A013262 A013267 A013268 * A326428 A260813 A062013
KEYWORD
nonn,easy
STATUS
approved