A235053 Numbers k of the form p^2 + 1 (for prime p) where k^2 + 1 is also prime.

10, 26, 170, 1850, 2210, 16130, 69170, 76730, 85850, 113570, 120410, 157610, 196250, 218090, 237170, 253010, 332930, 351650, 368450, 452930, 528530, 537290, 597530, 734450, 786770, 822650, 1329410, 2036330, 2211170

Offset

1,1

Comments

Except for 26, all numbers are divisible by 10 and the tens digit is an odd number.

Links

Seiichi Manyama, Table of n, a(n) for n = 1..1000

Example

351650 = 593^2 + 1 (593 is prime) and 351650^2 + 1 is prime, so 351650 is a member of this sequence.

Prog

(Python)
import sympy
from sympy import isprime
{print(n**2+1) for n in range(10**7) if isprime(n) if isprime((n**2+1)**2+1)}

Crossrefs

Numbers in both A066872 and A005574.

Cf. A235982, A235983.

Sequence in context: A092774 A259979 A368503 * A217583 A301606 A281510

Adjacent sequences: A235050 A235051 A235052 * A235054 A235055 A235056

Keyword

nonn

Author

Derek Orr, Jan 03 2014

Status

approved