A027756 Numbers k such that k^2 + k + 7 is prime.

0, 2, 3, 5, 8, 9, 11, 12, 17, 18, 24, 26, 29, 30, 32, 33, 38, 39, 44, 50, 51, 57, 59, 65, 71, 74, 86, 89, 92, 95, 96, 99, 102, 108, 113, 122, 123, 128, 131, 134, 135, 137, 141, 143, 144, 156, 159, 164, 165, 170, 173, 176, 177, 180, 183, 198, 201, 206

Offset: 1

Author

Patrick De Geest

Keywords

• nonn
• easy

Links

• Harvey P. Dale, Table of n, a(n) for n = 1..1000
• P. De Geest, World!Of Numbers

Crossrefs

Cf. A005471 (associated primes).

Programs

Magma

[n: n in [0..250] | IsPrime(n^2+n+7)]; // Vincenzo Librandi, Nov 20 2010

Mathematica

Select[Range[0,250],PrimeQ[#^2+#+7]&] (* Harvey P. Dale, Oct 10 2011 *)

PARI

is(n)=isprime(n^2+n+7) \\ Charles R Greathouse IV, Feb 20 2017