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

Offset: 1

Author

Zdenek Cervenka, Oct 21 2017

Keywords

• nonn

Examples

			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.
		

Crossrefs

Cf. A000396, A048050.

Programs

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 *)