A068419 Odd prime values of sigma(k) - phi(k) taking k in increasing order.

5, 11, 7, 23, 11, 47, 79, 73, 67, 23, 191, 283, 383, 739, 47, 1459, 281, 607, 59, 1153, 1069, 3319, 83, 1801, 2671, 3517, 743, 107, 6679, 3529, 6619, 6143, 6271, 4153, 10169, 9817, 167, 6451, 179, 24097, 23539, 10369, 227, 263, 16369, 41203, 20809, 54919

Offset: 1

Author

Benoit Cloitre, Mar 02 2002

Keywords

• easy
• nonn

Examples

			sigma(2312) - phi(2312) = 3517 is prime, so is in the sequence.
		

Crossrefs

Cf. A051612.

Programs

PARI

lista(nn) = {for (k = 1, nn, if (isprime(p = (sigma(k) - eulerphi(k))) && (p % 2), print1(p, ", ")););} \\ Michel Marcus, Nov 24 2013

Extensions

Terms 3517, 10169, 9817 added by Michel Marcus, Nov 24 2013