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Search: id:A137972
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| A137972 |
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G.f. satisfies A(x) = 1 + x*(1 + x*A(x)^4)^6. |
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+0
6
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| 1, 1, 6, 39, 320, 2787, 25788, 247731, 2449188, 24753960, 254610962, 2656496133, 28046838948, 299085697722, 3216723340218, 34852657892685, 380063012970680, 4168108473073596, 45941874232280862, 508664757809869052
(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 A137971.
a(n) = Sum_{k=0..n-1} C(6*(n-k),k)/(n-k) * C(4*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^4)^6); polcoeff(A, n)}
(PARI) a(n)=if(n==0, 1, sum(k=0, n-1, binomial(6*(n-k), k)/(n-k)*binomial(4*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. A137971, A137973; A137968, A137970, A137974.
Sequence in context: A009018 A135890 A067273 this_sequence A007322 A058191 A113347
Adjacent sequences: A137969 A137970 A137971 this_sequence A137973 A137974 A137975
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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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