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Search: id:A026597
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| 1, 2, 6, 14, 38, 94, 246, 622, 1606, 4094, 10518, 26894, 68966, 176542, 452406, 1158574, 2968198, 7602494, 19475286, 49885262, 127786406, 327327454, 838473078, 2147782894, 5501675206, 14092806782, 36099507606, 92470734734
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OFFSET
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0,2
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COMMENT
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This sequence can generated by the following formula: a(n) = a(n-1) + 4*a(n-2) when n > 2; a[1] = 1, a[2] = 2. - Alex Vinokur (alexvn(AT)barak-online.net), Oct 21 2004
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FORMULA
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G.f.: (1+x)/(1-x-4x^2).
a(n)=sum{k=0..n, binomial(floor((2n-k-1)/2), n-k)2^k} - Paul Barry (pbarry(AT)wit.ie), Feb 11 2005
a(n) = A006131(n)+A006131(n-1), n>=1. - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Oct 20 2006
a(n)=sum{k=0..n, C(floor((2n-k)/2),n-k)*4^floor(k/2)} - Paul Barry (pbarry(AT)wit.ie), Feb 02 2007
Inverse binomial transform of A007482: (1, 3, 11, 39, 139, 495,...). - Gary W. Adamson (qntmpkt(AT)yahoo.com), Dec 04 2007
a(n)=Sum_{k, 0<=k<=n+1}A122950(n+1,k)*3^(n+1-k) . - Philippe DELEHAM (kolotoko(AT)wanadoo.fr), Jan 04 2008
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CROSSREFS
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Cf. A006131, A026581, A006138.
Cf. A007482.
Sequence in context: A006864 A071636 A100067 this_sequence A122112 A000634 A006654
Adjacent sequences: A026594 A026595 A026596 this_sequence A026598 A026599 A026600
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KEYWORD
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nonn
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AUTHOR
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Clark Kimberling (ck6(AT)evansville.edu)
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