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Search: id:A107104
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| 1, 2, 6, 26, 154, 1182, 11254, 128522, 1715802, 26251118, 453132214, 8714516538, 184817376154, 4285657717694, 107880712446966, 2929921866938858, 85399256991014746, 2659096654189212558, 88091786616208073398
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OFFSET
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0,2
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FORMULA
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a(n) = 2*A043301(n-1) = 2^n*Sum_{k=0..n-1}(n+k-1)!/(n-k-1)!/k!/4^k for n>0, with a(0) = 1.
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PROGRAM
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(PARI) a(n)=if(n==0, 1, 2^n*sum(k=0, n-1, (n+k-1)!/(n-k-1)!/k!/4^k)) (PARI) {a(n)=local(X=x+x*O(x^n), Y=y+y*O(y^n)); sum(k=0, n, abs((matrix(n+1, n+1, m, j, if(m>=j, (m-1)!*polcoeff(polcoeff(exp(X+Y*X^2/2+X*Y), m-1, x), j-1, y)))^-1)[n+1, k+1]))}
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CROSSREFS
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Cf. A100862, A043301, A107102, A107103.
Adjacent sequences: A107101 A107102 A107103 this_sequence A107105 A107106 A107107
Sequence in context: A032187 A003659 A032271 this_sequence A123306 A099758 A099760
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KEYWORD
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nonn
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AUTHOR
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Paul D. Hanna (pauldhanna(AT)juno.com), May 21 2005
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