A336463 - OEIS

%I #5 Jul 24 2020 10:58:37

%S 1,2,4,7,8,14,15,16,21,28,33,42,45,56,60,64,84,102,112,128,130,132,

%T 147,152,160,168,180,240,273,306,336,406,408,435,441,448,512,513,520,

%U 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 Numbers k for which A335915(k) = A335915(sigma(sigma(k))).

%C Numbers k such that A335915(k) = A336456(k).

%C See comments in A336464.

%H <a href="/index/O#opnseqs">Index entries for sequences where odd perfect numbers must occur, if they exist at all</a>

%o (PARI)

%o A000265(n) = (n>>valuation(n,2));

%o 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 isA336463(n) = (A335915(n)==A335915(sigma(sigma(n))));

%Y Cf. A000203, A000265, A335915, A336455, A336456.

%Y Cf. also A336461, A336462, A336464.

%K nonn

%O 1,2

%A _Antti Karttunen_, Jul 22 2020