A242929 Primes p such that 2^p - p^2 is prime.

5, 7, 17, 19, 53, 83, 227, 461, 2221, 3547, 9029, 119087

Offset: 1

Author

Juri-Stepan Gerasimov, May 27 2014

Keywords

• nonn
• more

Comments

a(12) > 23053. - Robert Israel, Jun 10 2014

Examples

			5 is in this sequence because 5 and 2^5 - 5^2 = 7 are both prime.
		

Crossrefs

Cf. A098105, A117587.

Subsequence of A072180.

Programs

Magma

[p: p in PrimeUpTo(2200) | IsPrime(2^p - p^2)];

Maple

select(p -> isprime(p) and isprime(2^p - p^2), {2} union {seq(2*i+1,i=1..2000)});# Robert Israel, Jun 10 2014

Mathematica

Select[Prime[Range[300]], PrimeQ[2^# - #^2] &] (* Alonso del Arte, May 27 2014 *)

PARI

isok(p) = isprime(p) && ispseudoprime(2^p - p^2); \\ Daniel Suteu, Jun 25 2022

Formula

a(n) = prime(A117587(n)). - Daniel Suteu, Jun 25 2022

Extensions

a(9) from Alonso del Arte, May 27 2014

a(10) from Alois P. Heinz, May 28 2014

a(11) from Robert Israel, Jun 10 2014

a(12) added by Daniel Suteu, Jun 25 2022