A164623 Primes p such that p*(p-1)/2-5 and p*(p-1)/2+5 are also prime numbers.
13, 157, 673, 1069, 1117, 1153, 1213, 1597, 2029, 2089, 2437, 2713, 2833, 3613, 4057, 4909, 5653, 6337, 6529, 7549, 7993, 8053, 9613, 10789, 11497, 11689, 12073, 12373, 13309, 13669, 13789, 14173, 15289, 15937, 16249, 18097, 18637, 19249, 19993
Offset: 1
Examples
13 is in the sequence because 13*6-5=73 and 13*6+5=83 are both prime.
Links
- Vincenzo Librandi, Table of n, a(n) for n = 1..1000
Crossrefs
Programs
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Mathematica
Select[Prime[Range[2300]], PrimeQ[# (# - 1)/2 - 5] && PrimeQ[# (# - 1)/2 + 5] &]
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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 */
Extensions
Edited by R. J. Mathar, Aug 20 2009
Mathematica code adapted to the definition by Bruno Berselli, Apr 10 2013
Comments