A292714 Composite numbers k such that phi(x) = psi(k)*phi(k) has no solution.

2197, 4934, 5386, 7606, 10774, 11434, 15212, 15214, 15634, 16294, 17146, 18134, 18374, 18994, 19466, 20134, 20362, 23194, 23451, 24051, 24874, 25526, 25934, 26326, 27411, 27561, 27994, 28486, 28561, 30034, 31334, 31366, 36748, 37834, 38074, 40694, 44054, 46234, 47494, 49834

Offset

1,1

Comments

Or composite numbers k such that A007434(k) is not a totient number (A002202).

Prime power terms are 13^3, 13^4, 353^2, 457^2, 733^2, 877^2, 997^2, ...

Links

Amiram Eldar, Table of n, a(n) for n = 1..10000

Example

4934 = 2*2467 is a term because psi(4934)*phi(4934) = (2^2 - 1)*(2467^2 - 1) = 2^3*3^3*137*617 is not a totient number (A002202).

Prog

(PARI) is(k) = if(isprime(k), 0, my(f = factor(k)); !istotient(prod(i = 1, #f~, (f[i, 1]^2 - 1) * f[i, 1]^(2*f[i, 2] - 2)))); \\ Amiram Eldar, Dec 05 2024

Crossrefs

Cf. A000010, A001615, A002202, A007434, A281958.

Sequence in context: A342428 A229319 A109408 * A202459 A017535 A180693

Adjacent sequences: A292711 A292712 A292713 * A292715 A292716 A292717

Keyword

nonn

Author

Altug Alkan, Sep 21 2017

Status

approved