A293992 - OEIS

A293992

Numbers k such that sigma(k) - k - 1 is a perfect number.

8, 115, 187, 1375, 2455, 8143, 13543, 18261, 21103, 23479, 40615, 41623, 43279, 49183, 49441, 51703, 56743, 61063, 61279, 61423, 89287, 95551, 137887, 214303, 331567, 379807, 476071, 715471, 1422871, 1515967, 1793527, 1977127, 2431087, 3098527, 3663871

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OFFSET

1,1

LINKS

Table of n, a(n) for n=1..35.

EXAMPLE

sigma(8) - 8 - 1 = 6, a perfect number, so 8 is a term;

sigma(115) - 115 - 1 = 28, a perfect number, so 115 is a term.

MATHEMATICA

With[{pn=PerfectNumber[Range[10]]}, Select[Range[37*10^5], MemberQ[pn, DivisorSigma[ 1, #]-#-1]&]] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Feb 04 2019 *)

CROSSREFS

Cf. A000396, A048050.

Sequence in context: A113670 A347019 A156468 * A220575 A240890 A241105

Adjacent sequences: A293989 A293990 A293991 * A293993 A293994 A293995

KEYWORD

nonn

AUTHOR

Zdenek Cervenka, Oct 21 2017

STATUS

approved