A007636 Numbers k such that k^2 + k + 17 is composite.

16, 17, 20, 25, 32, 33, 34, 36, 39, 41, 43, 48, 50, 51, 52, 54, 55, 58, 61, 65, 66, 67, 68, 69, 71, 74, 77, 78, 80, 83, 84, 85, 88, 89, 90, 93, 94, 96, 97, 99, 100, 101, 102, 105, 106, 107, 111, 112, 115, 116, 117, 118, 119, 122, 124, 126, 131, 134, 135, 136, 137

Offset: 1

Author

N. J. A. Sloane, Mira Bernstein, Robert G. Wilson v

Keywords

• nonn
• easy

Comments

Complement of A028823. - Michel Marcus, Jun 17 2013

References

• N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Links

• Vincenzo Librandi, Table of n, a(n) for n = 1..3500

Programs

Magma

[n: n in [0..200]| not IsPrime(n^2+n+17)]; // Vincenzo Librandi, Jun 08 2017

Mathematica

Select[Range[200], !PrimeQ[#^2 + # + 17] &] (* Vincenzo Librandi, Jun 08 2017 *)