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Search: id:A108475
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| A108475 |
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Expansion of (1-3x)/(1-5x-5x^2+x^3). |
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+0
4
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| 1, 2, 15, 84, 493, 2870, 16731, 97512, 568345, 3312554, 19306983, 112529340, 655869061, 3822685022, 22280241075, 129858761424, 756872327473, 4411375203410, 25711378892991, 149856898154532, 873430010034205
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OFFSET
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0,2
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COMMENT
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Row sums of A108477. In general, sum{k=0..n, sum{j=0..n, C(2(n-k),j)C(2k,j)r^j}} has expansion (1-(r+1)x)/((1+(r+3)x+(r-1)(r+3)x^2+(r-1)^3*x^3).
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FORMULA
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G.f.: (1-3x)/((1+x)(1-6x+x^2)); a(n)=5a(n-1)+5a(n-2)-a(n-3); a(n)=sum{k=0..n, sum{j=0..n, C(2(n-k), j)C(2k, j)2^j}}.
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CROSSREFS
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Sequence in context: A109725 A057152 A002740 this_sequence A098624 A116079 A037746
Adjacent sequences: A108472 A108473 A108474 this_sequence A108476 A108477 A108478
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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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