A336463 Numbers k for which A335915(k) = A335915(sigma(sigma(k))).

1, 2, 4, 7, 8, 14, 15, 16, 21, 28, 33, 42, 45, 56, 60, 64, 84, 102, 112, 128, 130, 132, 147, 152, 160, 168, 180, 240, 273, 306, 336, 406, 408, 435, 441, 448, 512, 513, 520, 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

Offset: 1

Author

Antti Karttunen, Jul 22 2020

Keywords

• nonn

Comments

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

See comments in A336464.

Links

• Index entries for sequences where odd perfect numbers must occur, if they exist at all

Crossrefs

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

Cf. also A336461, A336462, A336464.

Programs

PARI

A000265(n) = (n>>valuation(n,2));
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]))); };
isA336463(n) = (A335915(n)==A335915(sigma(sigma(n))));