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 A088834 #48 Jul 28 2025 06:12:40 %S A088834 1,5,6,25,180,8925,32445,442365 %N A088834 Numbers k such that sigma(k) == 6 (mod k). %C A088834 For each integer j in A059609, 2^(j-1)*(2^j - 7) is in the sequence. E.g., for j = A059609(1) = 39 we get 151115727449904501489664. - _M. F. Hasler_ and _Farideh Firoozbakht_, Dec 03 2013 %C A088834 No more terms to 10^10. - _Charles R Greathouse IV_, Dec 05 2013 %C A088834 a(9) > 10^13. - _Giovanni Resta_, Apr 02 2014 %C A088834 a(9) > 1.5*10^14. - _Jud McCranie_, Jun 02 2019 %C A088834 No more terms < 2.7*10^15. - _Jud McCranie_, Jul 27 2025 %H A088834 Farideh Firoozbakht and M. F. Hasler, <a href="https://cs.uwaterloo.ca/journals/JIS/VOL13/Hasler/hasler2.html">Variations on Euclid's formula for perfect numbers</a>, Journal of Integer Sequences 13 (2010), 18 pp. Article ID 10.3.1. %e A088834 Sigma(25) = 31 = 1*25 + 6, so 31 mod 25 = 6. %t A088834 Select[Range[1000000], Mod[DivisorSigma[1, #] - 6, #] == 0 &] (* _T. D. Noe_, Dec 03 2013 *) %o A088834 (PARI) isok(n) = Mod(sigma(n), n) == 6; \\ _Michel Marcus_, Jan 03 2023 %Y A088834 Cf. A054024, A045768, A045769, A045770, A077374, A076496, A088012. %Y A088834 Cf. A087167 (a subsequence). %Y A088834 Cf. A059609. %K A088834 nonn,more %O A088834 1,2 %A A088834 _Labos Elemer_, Oct 29 2003 %E A088834 Terms corrected by _Charles R Greathouse IV_ and _Farideh Firoozbakht_, Dec 03 2013