A127435 - OEIS

%I #13 Nov 21 2020 14:46:39

%S 2,3,5,7,11,17,37,41,67,127,131,151,157,181,211,241,251,257,271,281,

%T 307,397,401,421,431,467,491,557,571,577,647,691,701,751,761,827,907,

%U 911,937,947,967,1061,1097,1151,1277,1291,1307,1321,1367,1567,1571,1861

%N Primes p such that (p-1)^2 + 1 is prime.

%C Consists of 3 and a subsequence of A045349.

%C These are the primes of the form A067720(k)+1. - _Michel Marcus_, Nov 21 2020

%F a(n) = sqrt(A127436(n)-1) + 1.

%t Select[Prime@Range[300], PrimeQ[(# - 1)^2 + 1] &] (* _Ray Chandler_, Jan 23 2007 *)

%o (PARI) listp(nn) = {forprime(p=2, nn, if (isprime((p-1)^2 + 1), print1(p, ", ")););} \\ _Michel Marcus_, Jun 08 2016

%Y For the associated primes, see A127436.

%Y Cf. A045349, A067720.

%K nonn

%O 1,1

%A _Lekraj Beedassy_, Jan 14 2007

%E Corrected and extended by _Ray Chandler_, Jan 23 2007