login
A068419
Odd prime values of sigma(k) - phi(k) taking k in increasing order.
0
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
1,1
EXAMPLE
sigma(2312) - phi(2312) = 3517 is prime, so is in the sequence.
PROG
(PARI) lista(nn) = {for (k = 1, nn, if (isprime(p = (sigma(k) - eulerphi(k))) && (p % 2), print1(p, ", ")); ); } \\ Michel Marcus, Nov 24 2013
CROSSREFS
Cf. A051612.
Sequence in context: A226606 A226619 A367705 * A226586 A368055 A358613
KEYWORD
easy,nonn
AUTHOR
Benoit Cloitre, Mar 02 2002
EXTENSIONS
Terms 3517, 10169, 9817 added by Michel Marcus, Nov 24 2013
STATUS
approved