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Search: id:A155020
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| A155020 |
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a(n)=2*a(n-1)+2*a(n-2), n>2 ; a(0)=1, a(1)=1, a(2)=3 . |
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+0
2
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| 1, 1, 3, 8, 22, 60, 164, 448, 1224, 3344, 9136, 24960, 68192, 186304, 508992, 1390592, 3799168, 10379520, 28357376, 77473792, 211662336, 578272256, 1579869184, 4316282880, 11792304128, 32217174016
(list; graph; listen)
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OFFSET
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0,3
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FORMULA
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G.f.: (1-x-x^2)/(1-2*x-2*x^2) . a(n+1)=Sum_{k, 0<=k<=n}A154929(n,k)=A028859(n) .
a(n)=(1/3)*sqrt(3)*{[1+sqrt(3)]^(n-1)-[1-sqrt(3)]^(n-1)}+(1/2)*{[1+sqrt(3)]^(n-1)+[1-sqrt(3)]^(n-1)}+(1/2)*[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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Equals 1 followed by A028859. [From Klaus Brockhaus (klaus-brockhaus(AT)t-online.de), Jul 18 2009]
Sequence in context: A055887 A024581 A028859 this_sequence A014397 A048503 A048579
Adjacent sequences: A155017 A155018 A155019 this_sequence A155021 A155022 A155023
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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 19 2009
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