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Search: id:A155117
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| A155117 |
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a(n)=4*a(n-1)+4*a(n-2), n>2 ; a(0)=1, a(1)=3, a(2)=15 . |
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1
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| 1, 3, 15, 72, 348, 1680, 8112, 39168, 189120, 913152, 4409088, 21288960, 102792192, 496324608, 2396467200, 11571167232, 55870537728, 269766819840, 1302549430272, 6289265000448, 30367257722880, 146626090893312
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OFFSET
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0,2
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FORMULA
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G.f.: (1-x-x^2)/(1-4*x-4*x^2) . a(n)=3*A086347(n), n>=1 .
a(n)=(3/2)*{[2+2*sqrt(2)]^(n-1)+[2-2*sqrt(2)]^(n-1)}+(9/8)*sqrt(2)*{[2+2*sqrt(2)]^(n-1)-[2-2*sqrt(2)]^(n-1)}+(1/4)*[C(2*n,n) mod 2], with n>=0 [From Paolo P. Lava (ppl(AT)spl.at), Jan 26 2009]
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CROSSREFS
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Sequence in context: A033876 A009174 A123942 this_sequence A137638 A156019 A145839
Adjacent sequences: A155114 A155115 A155116 this_sequence A155118 A155119 A155120
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KEYWORD
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nonn
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AUTHOR
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Philippe DELEHAM (kolotoko(AT)wanadoo.fr), Jan 20 2009
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