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%I #37 Oct 25 2024 15:38:31
%S 1,2,6,12,24,36,42,70,126,132,144,168,210,225,252,336,344,378,385,396,
%T 462,504,528,546,560,561,576,627,630,660,672,693,714,798,896,924,930,
%U 945,960,1001,1008,1012,1032,1050,1116
%N Numbers k such that sigma(2^k+1) == 0 (mod k).
%C 1155 is also a term. - _Husnain Raza_, Oct 23 2024
%H Husnain Raza, <a href="https://github.com/epistemologist/OEIS_Sequences/tree/main/A067718">Github link</a>
%t Select[Range[150], Divisible[DivisorSigma[1, 2^# + 1], #] &] (* _Amiram Eldar_, Nov 28 2020 *)
%o (PARI) isok(n)=sigma(2^n+1)%n==0 \\ _Klaus Brockhaus_, Apr 13 2005
%Y Cf. A000051, A000203, A069061.
%K nonn,hard,more
%O 1,2
%A _Benoit Cloitre_, Feb 05 2002
%E a(13)-a(15) from _Klaus Brockhaus_, Apr 13 2005
%E a(16)-a(21) from _Lars Blomberg_, Jul 28 2017
%E a(22)-a(44) from _Amiram Eldar_, Nov 28 2020
%E a(45) from _Husnain Raza_, Sep 18 2024