This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A067702 #41 May 26 2025 09:56:58 %S A067702 12,70,88,180,1888,4030,5830,32128,521728,1848964,8378368,34359083008, %T A067702 66072609790,549753192448,259708613909470,2251799645913088 %N A067702 Numbers k such that sigma(k) == 0 (mod k+2). %C A067702 If 2^i-5 is prime for i > 2 then let x = (2^i-5)*2^(i-1). Then sigma(x)=2*(x+2), so x is in the sequence. There are other terms that are not of this form. - _Jud McCranie_, Jan 12 2019 %C A067702 Contains terms of A088832, terms m of A088834 with (sigma(m)-6)/m = 3, terms m of A045770 with (sigma(m)-8)/m = 4, terms m of A076496 with (sigma(m)-12)/m = 6. - _Max Alekseyev_, May 26 2025 %e A067702 sigma(180) = 546 = 3(180+2), so 180 is in the sequence. %t A067702 Select[Range[84*10^5],Divisible[DivisorSigma[1,#],#+2]&] (* _Harvey P. Dale_, May 11 2018 *) %o A067702 (PARI) isok(n) = sigma(n) % (n+2) == 0; \\ _Michel Marcus_, Nov 22 2013 %Y A067702 Contains subsequence A088832. %Y A067702 Cf. A045768, A156560, A059608, A045770, A076496, A088834. %K A067702 nonn,more %O A067702 1,1 %A A067702 _Benoit Cloitre_, Feb 05 2002 %E A067702 a(9)-a(11) from _Michel Marcus_, Nov 22 2013 %E A067702 a(12)-a(13) from _Jud McCranie_, Jan 12 2019 %E A067702 a(14) from _Jud McCranie_, Jan 13 2019 %E A067702 a(15) from _Jud McCranie_, Dec 02 2019 %E A067702 a(16) from _Max Alekseyev_, May 26 2025