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Search: id:A098455
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| A098455 |
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Expansion of 1/sqrt(1-4x-36x^2). |
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+0
2
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| 1, 2, 24, 128, 1096, 7632, 60864, 461568, 3648096, 28551872, 226695424, 1799989248, 14380907776, 115126211072, 924791445504, 7444100947968, 60057602459136, 485388465196032, 3929580292706304, 31858982479331328
(list; graph; listen)
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OFFSET
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0,2
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COMMENT
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Define Q(n,x)=sum{k=0..floor(n/2), binomial(n,k)binomial(2(n-k),n)x^(n-2k)}. Then a(n)=3^n*Q(n,1/3). A084770(n) is 2^n*Q(n,1/2). Central coefficient of (1+2x+10x^2)^n.
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FORMULA
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E.g.f.: exp(2x)BesselI(0, 2sqrt(10)x); a(n)=sum{k=0..floor(n/2), binomial(n, k)binomial(2(n-k), n)9^k}.
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CROSSREFS
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Sequence in context: A034310 A060817 A045820 this_sequence A078994 A000185 A163752
Adjacent sequences: A098452 A098453 A098454 this_sequence A098456 A098457 A098458
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KEYWORD
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easy,nonn
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AUTHOR
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Paul Barry (pbarry(AT)wit.ie), Sep 08 2004
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