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Search: id:A108486
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| A108486 |
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Sum binomial(2n-2k,2k)3^k*2^(n-k), k=0..floor(n/2). |
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+0
2
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| 1, 2, 10, 80, 412, 2456, 14680, 85376, 503056, 2959136, 17381536, 102199040, 600757696, 3531251072, 20758107520, 122021457920, 717273440512, 4216334967296, 24784750512640, 145691471876096, 856414086962176
(list; graph; listen)
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OFFSET
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0,2
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COMMENT
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In general, sum{k=0..floor(n/2), C(2n-2k,2k)a^k*b^(n-k)} has expansion (1-bx-abx^2)/(1-2bx-(2ab-b^2)x^2-2ab^2*x^3+(ab)^2*x^4).
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FORMULA
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G.f.: (1-2x-6x^2)/(1-4x-8x^2-24x^3+36x^4); a(n)=4a(n-1)+8a(n-2)+24a(n-3)-36a(n-4).
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CROSSREFS
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Sequence in context: A098636 A081363 A100248 this_sequence A003578 A048286 A133480
Adjacent sequences: A108483 A108484 A108485 this_sequence A108487 A108488 A108489
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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), Jun 04 2005
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