A164623 - OEIS

%I #13 Oct 18 2014 14:12:04

%S 13,157,673,1069,1117,1153,1213,1597,2029,2089,2437,2713,2833,3613,

%T 4057,4909,5653,6337,6529,7549,7993,8053,9613,10789,11497,11689,12073,

%U 12373,13309,13669,13789,14173,15289,15937,16249,18097,18637,19249,19993

%N Primes p such that p*(p-1)/2-5 and p*(p-1)/2+5 are also prime numbers.

%C Primes A000040(k) such that A008837(k)+-5 are also prime numbers.

%H Vincenzo Librandi, <a href="/A164623/b164623.txt">Table of n, a(n) for n = 1..1000</a>

%e 13 is in the sequence because 13*6-5=73 and 13*6+5=83 are both prime.

%t Select[Prime[Range[2300]], PrimeQ[# (# - 1)/2 - 5] && PrimeQ[# (# - 1)/2 + 5] &]

%o (PARI) forprime(p=2,10^6,my(b=binomial(p,2));if(isprime(b-5)&isprime(b+5),print1(p,", "))); /* _Joerg Arndt_, Apr 10 2013 */

%Y Cf. A008846, A020882, A068228, A068229, A082539, A086519, A107159, A158708, A139494, A164620, A164621, A164622, A023203.

%K nonn,easy

%O 1,1

%A _Vladimir Joseph Stephan Orlovsky_, Aug 17 2009

%E Edited by _R. J. Mathar_, Aug 20 2009

%E Mathematica code adapted to the definition by _Bruno Berselli_, Apr 10 2013