A027754 Numbers k such that k^2 + k + 5 is prime.

0, 1, 2, 3, 6, 7, 11, 16, 17, 18, 21, 23, 27, 31, 32, 38, 42, 48, 51, 62, 67, 72, 73, 76, 77, 83, 86, 91, 93, 97, 108, 111, 116, 121, 126, 133, 136, 137, 146, 153, 158, 163, 172, 177, 182, 188, 191, 192, 193, 202, 212, 213, 216, 223, 226, 231, 247, 248

Offset

1,3

Links

Seiichi Manyama, Table of n, a(n) for n = 1..10000

Patrick De Geest, World!Of Numbers

Example

Since 3^2 + 3 + 5 = 17, which is prime, 3 is in the sequence.
Since 4^2 + 4 + 5 = 25 = 5^2, 4 is not in the sequence.

Mathematica

Select[Range[0, 499], PrimeQ[#^2 + # + 5] &] (* Alonso del Arte, Nov 28 2016 *)

Prog

(Magma) [n: n in [0..1000] |IsPrime(n^2+n+5)] // Vincenzo Librandi, Nov 20 2010

Crossrefs

Cf. A014556, A027755.

Sequence in context: A256976 A179019 A096578 * A092857 A062404 A032875

Adjacent sequences: A027751 A027752 A027753 * A027755 A027756 A027757

Keyword

nonn

Author

Patrick De Geest

Status

approved