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A133594
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a(n)=3*a(n-1)+12*a(n-2) for n>=3, a(0)=1, a(1)=3, a(2)=18 .
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1
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1, 3, 18, 90, 486, 2538, 13446, 70794, 373734, 1970730, 10396998, 54839754, 289283238, 1525926762, 8049179142, 42458658570, 223966125414, 1181402279082, 6231800342214, 32872228375626, 173398289233446, 914661608207850
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,2
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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 .
a(n)=(3/2)*[(3/2)-(1/2)*sqrt(57)]^(n-1)+(3/2)*[(3/2)+(1/2)*sqrt(57)]^(n-1)+(9/38)*sqrt(57)*[(3/2)+(1/2) *sqrt(57)]^(n-1)-(9/38)*sqrt(57)*[(3/2)-(1/2)*sqrt(57)]^(n-1),100)+(1/4)*[C(2*n,n) mod 2], with n>=0 [From Paolo P. Lava (paoloplava(AT)gmail.com), Nov 18 2008]
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CROSSREFS
| Sequence in context: A006568 A147518 A088336 * A092691 A064671 A058409
Adjacent sequences: A133591 A133592 A133593 * A133595 A133596 A133597
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KEYWORD
| easy,nonn
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AUTHOR
| Philippe DELEHAM (kolotoko(AT)wanadoo.fr), Dec 31 2007
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