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Search: id:A137971
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| A137971 |
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G.f. satisfies A(x) = 1 + x*(1 + x*A(x)^6)^4. |
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+0
6
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| 1, 1, 4, 30, 232, 2037, 18720, 179454, 1770380, 17864490, 183510672, 1912621814, 20175123732, 214980182783, 2310645275932, 25021270486830, 272717638241172, 2989549949264304, 32938634975109864, 364566094737276708
(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)^4 where B(x) is the g.f. of A137972.
a(n) = Sum_{k=0..n-1} C(4*(n-k),k)/(n-k) * C(6*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^6)^4); polcoeff(A, n)}
(PARI) a(n)=if(n==0, 1, sum(k=0, n-1, binomial(4*(n-k), k)/(n-k)*binomial(6*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. A137972, A137970; A137956, A137958, A137964.
Sequence in context: A084976 A000313 A082144 this_sequence A052604 A038225 A086452
Adjacent sequences: A137968 A137969 A137970 this_sequence A137972 A137973 A137974
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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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