A336461 Numbers k for which A335915(k) = A335915(sigma(k)).

1, 2, 3, 6, 20, 28, 40, 56, 60, 84, 120, 135, 160, 168, 176, 189, 224, 270, 304, 378, 480, 496, 528, 585, 672, 819, 912, 1170, 1372, 1488, 1638, 1836, 2156, 2744, 3025, 3672, 3724, 3780, 4116, 4312, 4572, 6050, 6076, 6468, 6525, 7448, 7560, 7956, 8128, 8232, 9075, 9144, 9225, 9261, 10224, 10880, 10976, 11172, 12152, 12936, 13050, 14144

Offset: 1

Author

Antti Karttunen, Jul 22 2020

Keywords

• nonn

Comments

Numbers k such that A335915(k) = A336455(k).

If terms x and y are present and gcd(x,y) = 1, then x*y is present also. This follows because both A335915 and A336455 are multiplicative sequences.

See also 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.

Subsequences: A000396, A005820.

Cf. also A336462, 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]))); };
isA336461(n) = (A335915(n)==A335915(sigma(n)));