login

Reminder: The OEIS is hiring a new managing editor, and the application deadline is January 26.

Odd prime values of sigma(k) - phi(k) taking k in increasing order.
0

%I #14 Jan 03 2017 02:27:37

%S 5,11,7,23,11,47,79,73,67,23,191,283,383,739,47,1459,281,607,59,1153,

%T 1069,3319,83,1801,2671,3517,743,107,6679,3529,6619,6143,6271,4153,

%U 10169,9817,167,6451,179,24097,23539,10369,227,263,16369,41203,20809,54919

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

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

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

%Y Cf. A051612.

%K easy,nonn

%O 1,1

%A _Benoit Cloitre_, Mar 02 2002

%E Terms 3517, 10169, 9817 added by _Michel Marcus_, Nov 24 2013