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A158441
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G.f.: A(x) = exp( Sum_{n>=1} sigma(n)*x^n/(1+x^n) /n ).
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0
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1, 1, 1, 3, 2, 4, 7, 7, 9, 14, 18, 20, 31, 34, 42, 61, 69, 83, 109, 127, 156, 203, 228, 276, 347, 404, 477, 591, 683, 801, 990, 1132, 1323, 1598, 1837, 2148, 2560, 2929, 3405, 4018, 4608, 5319, 6244, 7124, 8184, 9569, 10877, 12465, 14457, 16412, 18761, 21633
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,4
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FORMULA
| Euler transform of A048272. [From Vladeta Jovovic (vladeta(AT)eunet.yu), Mar 28 2009]
G.f.: 1/prod(n>=1, P(x^n)^((-1)^(n-1)) ) where P(x) = prod(k>=1, 1-x^k ), see Pari code. [Joerg Arndt, Jun 24 2011]
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PROG
| (PARI) {a(n)=if(n==0, 1, polcoeff(exp(sum(m=1, n, sigma(m)*x^m/(1+x^m+x*O(x^n))/m)), n))}
(PARI ) N=99; /* that many terms */
x='x+O('x^N);
gf=1/prod(n=1, N, eta(x^n)^((-1)^(n-1))); /* == 1 +x +x^2 +3*x^3 +2*x^4 +4*x^5 +... */
Vec(gf) /* show terms */ /* Joerg Arndt, Jun 24 2011 */
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CROSSREFS
| Cf. A006171, A000203.
Sequence in context: A105025 A129594 A170950 * A102787 A014193 A128885
Adjacent sequences: A158438 A158439 A158440 * A158442 A158443 A158444
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KEYWORD
| nonn
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AUTHOR
| Paul D. Hanna (pauldhanna(AT)juno.com), Mar 28 2009
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