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

1,1

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

Prog

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

Crossrefs

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

Sequence in context: A128364 A281924 A054574 * A016837 A226218 A294087

Adjacent sequences: A363368 A363369 A363370 * A363372 A363373 A363374

Keyword

nonn

Author

Michel Marcus, May 29 2023

Status

approved