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Search: id:A141761
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| 1, 1, 1, 2, 6, 26, 154, 1188, 11474, 134432, 1863168, 29936846, 548625820, 11315025894, 259733293774, 6574304470320, 182050022755386, 5477819548007438, 178054691097463354, 6220193033111607018
(list; graph; listen)
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OFFSET
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0,4
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COMMENT
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Also equals column 1 (shifted) of triangle A141760.
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FORMULA
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G.f.: 1/(1-x) = Sum_{n>=0} a(n) * x^n/(1+x)^{n*(n-1)/2}.
a(n) = 1 - Sum_{j=0..n-1} a(j) * (-1)^(n-j) * C(j(j-1)/2 + n-j-1, n-j) for n>0, with a(0)=1.
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PROGRAM
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(PARI) {a(n)=if(n==0, 1, 1 - sum(j=0, n-1, a(j)*(-1)^(n-j)*binomial(j*(j-1)/2+n-j-1, n-j)))}
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CROSSREFS
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Cf. A141760, A141762, A141763, A141764.
Sequence in context: A003659 A032271 A107104 this_sequence A123306 A099758 A099760
Adjacent sequences: A141758 A141759 A141760 this_sequence A141762 A141763 A141764
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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), Jul 18 2008
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