A058888 Number of terms in the set invphi(2*prime(n)), where prime(n) is the n-th prime.

4, 4, 2, 0, 2, 0, 0, 0, 2, 2, 0, 0, 2, 0, 0, 2, 0, 0, 0, 0, 0, 0, 2, 2, 0, 0, 0, 0, 0, 2, 0, 2, 0, 0, 0, 0, 0, 0, 0, 2, 2, 0, 2, 0, 0, 0, 0, 0, 0, 0, 2, 2, 0, 2, 0, 0, 0, 0, 0, 2, 0, 2, 0, 0, 0, 0, 0, 0, 0, 0, 0, 2, 0, 0, 0, 0, 0, 0, 0, 0, 2, 0, 2, 0, 0, 2, 0, 0, 0, 0, 0, 0, 0, 2, 0, 0, 2, 0, 0, 0, 0, 0, 0, 0, 0

Offset: 1

Author

Labos Elemer, Jan 08 2001

Keywords

• nonn

Examples

			The set invphi(2*3) = {7,9,14,18}. It has 4 terms, so a(2) = 4, while invphi(2*1601) = {3203,6406}, thus a(252) = 2.
		

Links

• Amiram Eldar, Table of n, a(n) for n = 1..10000 (terms 1..1000 from Donovan Johnson)
• Max Alekseyev, PARI/GP Scripts for Miscellaneous Math Problems (invphi.gp).

Crossrefs

Cf. A000010, A002202, A005277, A007617, A071629-A071634.

Programs

Maple

with(numtheory): [seq(nops(invphi(2*ithprime(i))),i=1..256)];

PARI

a(n) = invphiNum(2*prime(n)); \\ Amiram Eldar, Nov 07 2024, using Max Alekseyev's invphi.gp

Extensions

Offset corrected by Donovan Johnson, Apr 28 2013