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 A064607 #30 Mar 08 2024 09:02:17
%S A064607 1,2,7,151,257,1823,3048,5588,6875,7201,8973,24099,5249801,9177919,
%T A064607 18926164,70079434,78647747,705686794,2530414370,3557744074,
%U A064607 25364328389,32487653727,66843959963
%N A064607 Numbers k such that A064604(k) is divisible by k.
%C A064607 Analogous sequences for various arithmetical functions are A050226, A056650, A064605-A064607, A064610, A064611, A048290, A062982, A045345.
%C A064607 a(19) > 2*10^9. - _Donovan Johnson_, Jun 21 2010
%C A064607 a(24) > 10^11, if it exists. - _Amiram Eldar_, Jan 18 2024
%F A064607 (Sum_{j=1..k} sigma_4(j)) mod k = A064604(k) mod k = 0.
%e A064607 Adding 4th-power divisor-sums for j = 1..7 gives 1+17+82+273+626+1394+2402 = 4795 which is divisible by 7, so 7 is a term and the integer quotient is 655.
%t A064607 k = 1; lst = {}; s = 0; While[k < 1000000001, s = s + DivisorSigma[4, k]; If[ Mod[s, k] == 0, AppendTo[lst, k]; Print@ k]; k++]; lst (* _Robert G.Wilson v_, Aug 25 2011 *)
%Y A064607 Cf. A001159, A064604, A050226, A056650, A064605, A064606, A064610-A064612, A048290, A062982, A045345.
%K A064607 nonn,more
%O A064607 1,2
%A A064607 _Labos Elemer_, Sep 24 2001
%E A064607 a(13)-a(18) from _Donovan Johnson_, Jun 21 2010
%E A064607 a(19)-a(23) from _Amiram Eldar_, Jan 18 2024