A363371 a(n) is the least prime p for which (p-1)*phi(p^n) is a nontotient, where phi is the Euler totient function (A000010).

23, 11, 23, 11, 23, 11, 47, 11, 11, 23, 47, 23, 23, 23, 47, 47, 103, 103, 103, 103, 103, 103, 167, 103, 103, 103, 103, 103, 103, 103, 103, 103, 103, 179, 103, 103, 103, 103, 103, 103, 103, 103, 127, 103, 103, 103, 103, 103, 103, 103, 103, 103, 103, 127, 127, 103, 127, 127, 127

Offset: 1

Author

Michel Marcus, May 29 2023

Keywords

• nonn

Comments

Thus a(n) is the least prime p for which p-1=phi(p), a totient value, multiplied by phi(p^n), another totient value, gives a nontotient. There are several instances of these numbers in A361058.

Links

• Michel Marcus, Table of n, a(n) for n = 1..160

Crossrefs

Cf. A000010, A002202 (totient values) A005277 (nontotients), A361058.

Programs

PARI

a(n) = my(p=2); while (istotient((p-1)*eulerphi(p^n)), p = nextprime(p+1)); p;