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Search: id:A157019
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| A157019 |
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Sum_{d|n} binomial(n/d+d-2,d-1). |
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+0
6
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| 1, 2, 2, 4, 2, 8, 2, 10, 8, 12, 2, 34, 2, 16, 32, 38, 2, 62, 2, 92, 58, 24, 2, 210, 72, 28, 92, 198, 2, 394, 2, 274, 134, 36, 422, 776, 2, 40, 184, 1142, 2, 1178, 2, 618, 1232, 48, 2, 2634, 926, 1482, 308, 964, 2, 2972, 2004, 4610, 382, 60, 2, 8576, 2, 64, 6470, 5130
(list; graph; listen)
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OFFSET
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1,2
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COMMENT
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Equals row sums of triangle A156348. - Gary W. Adamson & Mats Granvik (qntmpkt(AT)yahoo.com), Feb 21 2009
a(n) = 2 iff n is prime.
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FORMULA
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G.f.: A(x) = Sum_{n>=1} x^n/(1 - x^n)^n. [From Paul D. Hanna (pauldhanna(AT)juno.com), Mar 01 2009]
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EXAMPLE
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a(4) = 4 = (1 + 2 + 0 + 1).
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MAPLE
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add( binomial(n/d+d-2, d-1), d=numtheory[divisors](n) ) ;
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PROGRAM
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(PARI) {a(n)=polcoeff(sum(m=1, n, x^m/(1-x^m+x*O(x^n))^m), n)} [From Paul D. Hanna (pauldhanna(AT)juno.com), Mar 01 2009]
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CROSSREFS
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Cf. A081543, A018818.
Cf. A156348, A156027, A157028, A157029
Sequence in context: A072478 A100577 A018818 this_sequence A067538 A096154 A084540
Adjacent sequences: A157016 A157017 A157018 this_sequence A157020 A157021 A157022
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KEYWORD
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easy,nonn
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AUTHOR
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R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Feb 21 2009
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