A136242 Numbers k among A008864 such that k^2 - k + 1 is prime.

3, 4, 6, 18, 42, 60, 72, 90, 102, 132, 168, 174, 294, 384, 678, 702, 744, 762, 774, 828, 840, 858, 912, 1092, 1098, 1164, 1182, 1194, 1218, 1374, 1428, 1488, 1560, 1584, 1710, 1812, 1848, 1932, 1974, 2130, 2274, 2310, 2340, 2412, 2664, 2730, 2790, 2958

Offset: 1

Author

Lekraj Beedassy, Dec 24 2007

Keywords

• nonn
• easy

Comments

See A053183 for the primes associated with a(n).

Links

• Amiram Eldar, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A008864, A053182, A053183, A136243.

Programs

Mathematica

Select[Prime[Range[500]] + 1, PrimeQ[#^2 - # + 1] &] (* Amiram Eldar, Apr 19 2024 *)

PARI

lista(pmax) = forprime(p=1, pmax, if(isprime(p^2+p+1), print1(p+1, ", "))); \\ Amiram Eldar, Apr 19 2024

Formula

a(n) = A053182(n) + 1.