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 A336463 #5 Jul 24 2020 10:58:37 %S A336463 1,2,4,7,8,14,15,16,21,28,33,42,45,56,60,64,84,102,112,128,130,132, %T A336463 147,152,160,168,180,240,273,306,336,406,408,435,441,448,512,513,520, %U A336463 528,546,574,588,615,720,765,896,960,1023,1026,1224,1323,1344,1470,1568,1740,1764,1785,1989,2052,2112,2184,2296,2352,2432,2625 %N A336463 Numbers k for which A335915(k) = A335915(sigma(sigma(k))). %C A336463 Numbers k such that A335915(k) = A336456(k). %C A336463 See comments in A336464. %H A336463 <a href="/index/O#opnseqs">Index entries for sequences where odd perfect numbers must occur, if they exist at all</a> %o A336463 (PARI) %o A336463 A000265(n) = (n>>valuation(n,2)); %o A336463 A335915(n) = { my(f=factor(n)); prod(k=1,#f~,if(2==f[k,1],1,(A000265((f[k,1]^2)-1)^f[k,2]))); }; %o A336463 isA336463(n) = (A335915(n)==A335915(sigma(sigma(n)))); %Y A336463 Cf. A000203, A000265, A335915, A336455, A336456. %Y A336463 Cf. also A336461, A336462, A336464. %K A336463 nonn %O A336463 1,2 %A A336463 _Antti Karttunen_, Jul 22 2020