A245048 Primes p such that p^2 + 28 is prime.

3, 5, 11, 13, 17, 19, 23, 41, 43, 47, 53, 67, 79, 83, 89, 97, 109, 131, 137, 149, 157, 163, 167, 179, 181, 193, 211, 223, 239, 241, 251, 263, 277, 281, 311, 317, 331, 379, 397, 401, 409, 421, 431, 439, 443, 449, 457, 467, 479, 541, 569, 599, 643, 647, 673

Offset: 1

Author

Chai Wah Wu, Jul 10 2014

Keywords

• nonn

Comments

7 of the first 8 odd primes are in this list.

Examples

			3 is in the sequence because 3^2 + 28 = 37, which is also prime.
5 is in the sequence because 5^2 + 28 = 53, which is also prime.
7 is not in the sequence because 7^2 + 28 = 77 = 7 * 11.
		

Links

• Chai Wah Wu, Table of n, a(n) for n = 1..2000

Crossrefs

Cf. A062324 (p^2+4), A062718(p^2+6), A243367(p^2+10).

Programs

Maple

A245048:=n->`if`(isprime(n) and isprime(n^2+28), n, NULL): seq(A245048(n), n=1..10^3); # Wesley Ivan Hurt, Jul 24 2014

Mathematica

Select[Prime[Range[200]], PrimeQ[#^2 + 28] &] (* Alonso del Arte, Jul 12 2014 *)

Python

import sympy
[sympy.prime(n) for n in range(1,10**6) if sympy.ntheory.isprime(sympy.prime(n)**2+28)]