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A227988
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Decimal expansion of Sum_{n >= 1} sigma_1(n)/n!.
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4
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3, 5, 2, 7, 0, 0, 0, 4, 7, 1, 8, 5, 2, 9, 5, 2, 8, 2, 9, 7, 6, 1, 5, 3, 6, 7, 9, 1, 7, 6, 9, 3, 2, 6, 2, 0, 3, 7, 6, 3, 5, 6, 4, 3, 4, 4, 9, 5, 2, 4, 0, 8, 2, 7, 7, 6, 0, 5, 7, 1, 7, 8, 2, 0, 6, 1, 9, 2, 1, 5, 4, 6, 3, 8, 0, 4, 1, 8, 8, 6, 1, 4, 8, 2, 3, 4, 1
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OFFSET
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1,1
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COMMENTS
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Problem No. 45 from P. Erdős (see the first reference). The problem is "is Sum_{n >= 1} sigma_k(n)/n! an irrational number where sigma_k(n) is the sum of the k-th power of divisors of n?" This property has been proved with k = 1 and 2 (see the second reference for the proof).
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LINKS
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P. Erdős & M. Kac, Problem 4518, Amer. Math. Monthly 60(1953) 47. Solution R. Breusch, 61 (1954) 264-265.
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EXAMPLE
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3.52700047185295282976153...
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MAPLE
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with(numtheory):Digits:=200: s:=evalf(sum('sigma(i)/i!', 'i'=1..500)):print(s):
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MATHEMATICA
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RealDigits[N[Sum[DivisorSigma[1, n]/n!, {n, 0, 500}], 200]][[1]]
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PROG
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CROSSREFS
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KEYWORD
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AUTHOR
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STATUS
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approved
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