A215141 Decimal expansion of Sum_{n>=1} (-1)^(n+1) / sigma(n)^n.

9, 0, 4, 2, 2, 6, 1, 3, 8, 2, 2, 8, 4, 3, 4, 5, 2, 1, 1, 4, 6, 2, 7, 4, 9, 6, 5, 6, 2, 5, 6, 5, 6, 2, 7, 3, 2, 8, 7, 5, 1, 8, 2, 8, 3, 4, 9, 0, 3, 8, 1, 7, 6, 7, 3, 5, 9, 9, 7, 9, 1, 0, 9, 8, 7, 5, 8, 3, 2, 8, 2, 4, 3, 4, 7, 8, 8, 1, 4, 3, 0, 3, 6, 0, 5, 6, 8

Offset: 0

Author

Michel Lagneau, Aug 04 2012

Keywords

• nonn
• cons

Examples

			.90422613822843452114627...
		

Links

• G. C. Greubel, Table of n, a(n) for n = 0..5000

Crossrefs

Cf. A000203, A215140.

Programs

Mathematica

RealDigits[N[Sum[((-1)^(n+1))/DivisorSigma[1,n]^n,{n,1,105}],105]][[1]]

PARI

suminf(n=1, (-1)^(n+1)/sigma(n)^n) \\ Michel Marcus, Apr 20 2018