A087268 Solutions to gcd(x, pi(x)) = 1, where pi is A000720.

1, 2, 3, 5, 7, 9, 11, 12, 13, 17, 18, 19, 21, 23, 25, 26, 28, 29, 31, 32, 34, 35, 36, 37, 41, 42, 43, 45, 47, 49, 52, 53, 55, 57, 59, 60, 61, 65, 67, 68, 69, 70, 71, 73, 74, 76, 79, 81, 83, 84, 85, 86, 87, 88, 89, 91, 95, 97, 98, 99, 101, 103, 104, 106, 107, 109, 110, 111

Offset: 1

Author

Labos Elemer, Sep 16 2003

Keywords

• nonn

Examples

			All primes are included.
		

Links

• Ivan Neretin, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A007053, A000720, A087266, A087267, A057809.

Programs

Mathematica

Flatten[Position[Table[GCD[w, PrimePi[w]], {w, 1, 256}], 1]]

PARI

isok(n) = gcd(n, primepi(n)) == 1; \\ Michel Marcus, Apr 22 2018