A091568 Primes of the form p^2 - p - 1, where p is prime.

5, 19, 41, 109, 271, 811, 929, 2161, 3659, 4421, 4969, 9311, 10099, 16001, 17029, 19181, 22051, 32579, 38611, 57839, 72091, 93941, 109229, 128521, 143261, 157211, 166871, 175141, 176819, 201151, 208391, 228961, 236681, 240589, 358201, 367841

Offset: 1

Author

T. D. Noe, Jan 21 2004

Keywords

• nonn

Links

• Vincenzo Librandi, Table of n, a(n) for n = 1..5000

Crossrefs

Cf. A091567 (p such that p^2 - p - 1 is prime).

Programs

Mathematica

lst={};Do[p=Prime[n];p=p^2-p-1;If[PrimeQ[p],AppendTo[lst,p]],{n,3*5!}];lst (* Vladimir Joseph Stephan Orlovsky, Jan 27 2009 *)
Select[#^2-#-1&/@Prime[Range[200]],PrimeQ] (* Harvey P. Dale, May 15 2016 *)

PARI

isA091568(n)={local(i);i=floor((1/2)+sqrt(n+(5/4)));isprime(i) && n==i^2-i-1 && isprime(n)} \\ Michael B. Porter, May 12 2010