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 A128062 a(n) = denominator of b(n), where sum{m>=0} b(m)*x^m/m! = x/(sum(m>=1} H(m) x^m/ m!) = exp(-x)*x/(sum{m>=1} x^m (-1)^(m+1)/(m!*m)). (H(m) = sum{k=1 to m} 1/k.). 1
 1, 4, 72, 96, 21600, 17280, 5080320, 322560, 326592000, 145152000, 63228211200, 22992076800, 1298164008960000, 292919058432000, 11298306539520000, 273898340352000, 48978158848819200000, 886482513100800000 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 LINKS FORMULA b(0)=1. b(n) = -sum{k=1 to n} binomial(n,k) H(k+1) b(n-k)/(k+1). EXAMPLE 1/(1 + x * 3/(2 * 2) + x^2 * 11/(6 * 6) + x^3 * 25/(12 * 24) +...) = 1 -x * 3/4 + x^2 * 37/72 -x^3 * 29/96 ... MATHEMATICA b[0] = 1; b[n_] := b[n] = -Sum[Binomial[n, k] *HarmonicNumber[k + 1]*b[n - k]/(k + 1), {k, n}]; Denominator[Array[b, 20, 0]] (*Chandler*) CROSSREFS Cf. A128061. Sequence in context: A133003 A161791 A132097 * A227248 A113839 A077112 Adjacent sequences:  A128059 A128060 A128061 * A128063 A128064 A128065 KEYWORD frac,nonn AUTHOR Leroy Quet, Feb 13 2007 EXTENSIONS Extended by Ray Chandler, Feb 19 2007 STATUS approved

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Last modified August 18 15:00 EDT 2019. Contains 326106 sequences. (Running on oeis4.)