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A154289
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Denominators of coefficients in expansion of 1/ ( Sum_{n>=1} ( x^(n - 1)/(2*n - 1)!! ) ).
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3
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1, 3, 45, 945, 14175, 93555, 638512875, 273648375, 44405668125, 194896477400625, 32157918771103125, 201717854109646875, 3028793579456347828125, 698952364489926421875, 564653660170076273671875, 5660878804669082674070015625, 7217620475953080409439269921875
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OFFSET
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0,2
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LINKS
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FORMULA
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G.f.: 1/( Sum_{n>=1}( x^(n - 1)/(2*n - 1)!! ) ) = sqrt(2/Pi) * sqrt(x))/ (exp(x/2) * erf(sqrt(x)/sqrt(2)).
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MATHEMATICA
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q[x_] = (Sqrt[2/Pi]*Sqrt[x])/ (E^(x/2)*Erf[Sqrt[x]/Sqrt[2]]) ;
Denominator[CoefficientList[Series[q[x], {x, 0, 30}], x]]
(* program improved by Bob Hanlon (hanlonr(AT)cox.net) *)
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PROG
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(PARI) lista(n) = { n++; x = z + z*O(z^n); P = 1/sum(m=1, n, (x^(m - 1)/prod(k=1, m, 2*k-1))); n--; for (i=0, n, print1(denominator(polcoeff(P, i, z)), ", " ); ); } \\ Michel Marcus, Apr 30 2013
(Sage)
R, C = [1], [1]+[0]*(len-1)
for n in (1..len-1):
for k in range(n, 0, -1):
C[k] = C[k-1] / (2*k+1)
C[0] = -sum(C[k] for k in (1..n))
R.append((C[0]).denominator())
return R
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CROSSREFS
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KEYWORD
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nonn,frac
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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