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Search: id:A137968
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| A137968 |
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G.f. satisfies A(x) = 1 + x*(1 + x*A(x)^2)^6. |
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+0
6
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| 1, 1, 6, 27, 158, 981, 6342, 42728, 295008, 2079882, 14908740, 108312873, 795836544, 5903472999, 44151306690, 332552305818, 2520416719368, 19207222744326, 147086508325056, 1131292622149352, 8735383810590486
(list; graph; listen)
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OFFSET
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0,3
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FORMULA
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G.f.: A(x) = 1 + x*B(x)^6 where B(x) is the g.f. of A137967.
a(n) = Sum_{k=0..n-1} C(6*(n-k),k)/(n-k) * C(2*k,n-k-1) for n>0 with a(0)=1. [From Paul D. Hanna (pauldhanna(AT)juno.com), Jun 16 2009]
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PROGRAM
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(PARI) {a(n)=local(A=1+x*O(x^n)); for(i=0, n, A=1+x*(1+x*A^2)^6); polcoeff(A, n)}
(PARI) a(n)=if(n==0, 1, sum(k=0, n-1, binomial(6*(n-k), k)/(n-k)*binomial(2*k, n-k-1))) [From Paul D. Hanna (pauldhanna(AT)juno.com), Jun 16 2009]
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CROSSREFS
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Cf. A137967, A137969; A137970, A137972, A137974.
Sequence in context: A038176 A104745 A018901 this_sequence A062512 A087297 A117336
Adjacent sequences: A137965 A137966 A137967 this_sequence A137969 A137970 A137971
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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), Feb 26 2008
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