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Search: id:A098335
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| A098335 |
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Expansion of 1/sqrt(1-4x+8x^2). |
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+0
3
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| 1, 2, 2, -4, -26, -68, -76, 184, 1222, 3308, 3772, -9656, -64676, -177448, -203992, 536176, 3607622, 9968972, 11510636, -30723416, -207302156, -575382392, -666187432, 1796105744, 12142184476, 33803271032
(list; graph; listen)
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OFFSET
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0,2
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COMMENT
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Central coefficients of (1+2x-x^2)^n. Binomial transform of A098331.
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REFERENCES
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Tony D. Noe, On the Divisibility of Generalized Central Trinomial Coefficients, Journal of Integer Sequences, Vol. 9 (2006), Article 06.2.7.
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FORMULA
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E.g.f. : exp(2x)BesselI(0, 2*I*x), I=sqrt(-1); a(n)=sum{k=0..floor(n/2), binomial(n, k)binomial(n-k, k)2^n(-4)^(-k)}.
a(n)=sum{k=0..floor(n/2), binomial(n, k)binomial(2(n-k), k)(-2)^k} - Paul Barry (pbarry(AT)wit.ie), Sep 08 2004
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CROSSREFS
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Sequence in context: A009541 A006829 A154594 this_sequence A049147 A067068 A032334
Adjacent sequences: A098332 A098333 A098334 this_sequence A098336 A098337 A098338
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KEYWORD
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easy,sign
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AUTHOR
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Paul Barry (pbarry(AT)wit.ie), Sep 03 2004
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