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 A324707 #10 Jul 17 2021 07:26:23 %S A324707 6,60,90,36720,47520,8173440,22276800,126463680,597542400,4201148160, %T A324707 287704872000,1632485836800 %N A324707 Tri-unitary perfect numbers: numbers k such that tsigma(k) = 2k, where tsigma(k) is the sum of the tri-unitary divisors of k (A324706). %C A324707 Also in the sequence is 21623407345626345971712000. %C A324707 a(13) > 5*10^12. - _Giovanni Resta_, Mar 14 2019 %e A324707 36720 is in the sequence since its sum of tri-unitary divisors is A324706(36720) = 73440 = 2 * 36720. %t A324707 f[p_, e_] := If[e == 3, (p^4-1)/(p-1), If[e==6, (p^8-1)/(p^2-1), p^e+1]]; tsigma[1]=1; tsigma[n_]:= Times @@ f @@@ FactorInteger[n]; Select[Range[50000], tsigma[#]==2# &] %Y A324707 Cf. A000396, A002827, A007357, A322486, A324706, A324708, A324709. %K A324707 nonn,more %O A324707 1,1 %A A324707 _Amiram Eldar_, Mar 11 2019 %E A324707 a(11)-a(12) from _Giovanni Resta_, Mar 14 2019