A248719 Numbers n such that 4*nextprime(2^n)^2+1 is prime.

0, 1, 2, 5, 6, 18, 43, 52, 106, 383, 417, 663, 849, 971

Offset

1,3

Comments

This sequence provides "simplest" examples of large primes of the form x^2+1, cf. A174246.

Links

Table of n, a(n) for n=1..14.

Example

a(1)=0 since nextprime(2^0)=2 and 4*2^2+1 = 17 is prime.

Mathematica

fQ[n_] := PrimeQ[ 4NextPrime[2^n]^2 + 1]; Select[ Range@ 3000, fQ] (* Robert G. Wilson v, Dec 27 2014 *)

Prog

(PARI) for(n=0, 9e9, ispseudoprime(4*nextprime(2^n)^2+1)&&print1(n", "))

Crossrefs

Cf. A174246.

Sequence in context: A202854 A274911 A282536 * A184594 A341756 A014454

Adjacent sequences: A248716 A248717 A248718 * A248720 A248721 A248722

Keyword

nonn

Author

M. F. Hasler, Oct 12 2014

Extensions

a(13) and a(14) from Robert G. Wilson v, Dec 27 2014

Status

approved