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A293992
Numbers k such that sigma(k) - k - 1 is a perfect number.
0
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
1,1
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
Sequence in context: A113670 A347019 A156468 * A220575 A240890 A241105
KEYWORD
nonn
AUTHOR
Zdenek Cervenka, Oct 21 2017
STATUS
approved