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A066768
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Sum_{d|n} binomial(2*d-2,d-1).
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1
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1, 3, 7, 23, 71, 261, 925, 3455, 12877, 48693, 184757, 705713, 2704157, 10401527, 40116677, 155120975, 601080391, 2333619351, 9075135301, 35345312513, 137846529751, 538258059199, 2104098963721, 8233431436745, 32247603683171
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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FORMULA
| G.f.: Sum_{n>=1} x^n/sqrt(1-4*x^n). [From Paul D. Hanna, Aug 23 2011]
Logarithmic derivative of A052854, the number of unordered forests on n nodes.
Equals A051731 * A000984, i.e. the inverse Mobius transform of A000984. - Gary W. Adamson (qntmpkt(AT)yahoo.com), Nov 09 2007
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PROG
| (PARI) a(n)=if(n<1, 0, sumdiv(n, d, binomial(2*d-2, d-1)))
(PARI) a(n)=polcoeff(sum(m=1, n, x^m/sqrt(1-4*x^m+x*O(x^n))), n) /* Paul D. Hanna */
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CROSSREFS
| Cf. A034731, A052854.
Cf. A051731, A000984.
Sequence in context: A045610 A045723 A140456 * A062241 A000229 A133435
Adjacent sequences: A066765 A066766 A066767 * A066769 A066770 A066771
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KEYWORD
| nonn
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AUTHOR
| Vladeta Jovovic (vladeta(AT)eunet.rs), Jan 17 2002
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