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A068078 Numbers n such that (sigma(n)+sigma(n+1))/n is an integer. 4
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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

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

MATHEMATICA

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

CROSSREFS

Cf. A067806, A068077.

Sequence in context: A218631 A166066 A232583 * A067806 A001446 A264671

Adjacent sequences:  A068075 A068076 A068077 * A068079 A068080 A068081

KEYWORD

nonn

AUTHOR

Dean Hickerson, Feb 16 2002

EXTENSIONS

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

STATUS

approved

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Last modified August 2 03:55 EDT 2021. Contains 346409 sequences. (Running on oeis4.)