A336462 Numbers k for which A335915(sigma(k)) = A335915(sigma(sigma(k))).

1, 2, 5, 12, 19, 24, 27, 28, 38, 39, 44, 54, 56, 59, 60, 65, 78, 83, 84, 87, 92, 95, 123, 124, 129, 133, 136, 143, 160, 167, 168, 178, 212, 223, 248, 258, 259, 266, 269, 276, 285, 288, 297, 308, 360, 393, 395, 413, 427, 429, 437, 446, 455, 473, 479, 501, 518, 522, 528, 555, 560, 581, 611, 612, 681, 738, 752, 755

Offset: 1

Author

Antti Karttunen, Jul 22 2020

Keywords

• nonn

Comments

Numbers k for which A336455(k) = A336455(sigma(k)) = A336456(k).

Numbers k such that sigma(k) is in A336461.

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, A336463, 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]))); };
isA336462(n) = (A335915(sigma(n))==A335915(sigma(sigma(n))));