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Search: id:A108487
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| A108487 |
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Sum binomial(2n-2k,2k)10^(n-k), k=0..floor(n/2). |
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+0
1
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| 1, 10, 110, 1600, 25100, 395000, 6201000, 97280000, 1526010000, 23938500000, 375525100000, 5890896000000, 92411011000000, 1449659710000000, 22740940010000000, 356739136000000000, 5596198360100000000
(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.: (1-10x-10x^2)/(1-20x-80x^2-200x^3+100x^4); a(n)=20a(n-1)+80a(n-2)+200a(n-3)-100a(n-4).
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CROSSREFS
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Sequence in context: A143749 A049398 A055530 this_sequence A099883 A146753 A020767
Adjacent sequences: A108484 A108485 A108486 this_sequence A108488 A108489 A108490
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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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