A068078 Numbers k such that (sigma(k)+sigma(k+1))/k is an integer.

1, 10, 34, 136, 169, 2402, 5329, 21004, 38184, 41164, 54722, 458010, 776112, 1060802, 5026562, 10800112, 11108164, 14366402, 65676408, 87026656, 102944992, 387999360, 1488668112, 4414086384, 10499710072, 28645019964

Offset: 1

Author

Dean Hickerson, Feb 16 2002

Keywords

• nonn

Comments

The quotient (sigma(a(n))+sigma(a(n)+1))/a(n) is equal to 3 or 4 for n <= 33 and equal to 5 for a(34) = 1170035543040. - Giovanni Resta, Apr 04 2014

Links

• Giovanni Resta, Table of n, a(n) for n = 1..34

Crossrefs

Cf. A067806, A068077.

Programs

Mathematica

For[n=1, True, n++, If[Mod[DivisorSigma[1, n]+DivisorSigma[1, n+1], n]==0, Print[n]]]

Extensions

a(22)-a(26) from Donovan Johnson, Jan 31 2009