login

Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).

Primes p such that A071568((p-1)/2) is also prime.
8

%I #14 Sep 08 2022 08:45:46

%S 3,5,7,11,13,17,19,31,37,43,59,61,79,83,89,97,107,109,113,139,149,167,

%T 191,233,241,263,271,293,307,311,337,359,373,383,439,443,479,487,491,

%U 523,557,617,641,647,659,673,683,701,733,757,811,829,853,857,859,877

%N Primes p such that A071568((p-1)/2) is also prime.

%C Primes p such that (p-1)^3/8+(p+1)/2 is also prime, i.e., in A095692.

%H Vincenzo Librandi, <a href="/A163422/b163422.txt">Table of n, a(n) for n = 1..1000</a>

%e p=3 is in the sequence because (3-1)^3/8+(3+1)/2=3 is prime.

%e p=5 is in the sequence because (5-1)^3/8+(5+1)/2=11 is prime.

%t f[n_]:=((n-1)/2)^3+((n+1)/2); lst={}; Do[p=Prime[n]; If[PrimeQ[f[p]], AppendTo[lst, p]], {n,6!}]; lst

%t Select[Prime[Range[180]], PrimeQ[(#-1)^3/8+(#+1)/2]&] (* _Harvey P. Dale_, Jan 05 2011 *)

%o (Magma) [p: p in PrimesUpTo(1000) | IsPrime((p^3-3*p^2+7*p+3) div 8)]; // _Vincenzo Librandi_, Apr 10 2013

%Y Cf. A162652, A163418, A163419, A163420, A163421.

%K nonn,easy

%O 1,1

%A _Vladimir Joseph Stephan Orlovsky_, Jul 27 2009

%E Definition rewritten by _R. J. Mathar_, Aug 17 2009