A241264 Numbers k such that 2*k^2 + 2*k - 41 is not a prime.

4, 13, 20, 24, 26, 30, 31, 32, 35, 36, 37, 38, 40, 41, 43, 47, 49, 51, 54, 55, 60, 62, 63, 64, 67, 70, 71, 72, 73, 75, 76, 78, 79, 81, 82, 84, 85, 88, 89, 92, 94, 97, 98, 100, 102, 105, 108, 109, 111, 112, 113, 114, 115, 117, 118, 119, 120, 122, 123, 124, 125

Offset

1,1

Links

Vincenzo Librandi, Table of n, a(n) for n = 1..5000

Example

13 is in this sequence because 2*13^2 + 2*13 - 41 = 323 = 17*19.

Mathematica

Select[Range[4, 200], ! PrimeQ[2 #^2 + 2 # - 41] &]

Prog

(Magma) [n: n in [1..150] | not IsPrime(2*n^2+2*n-41)];

Crossrefs

Complement of A155771.

Sequence in context: A141491 A292363 A119048 * A066993 A297884 A298289

Adjacent sequences: A241261 A241262 A241263 * A241265 A241266 A241267

Keyword

nonn,easy

Author

Vincenzo Librandi, Apr 20 2014

Status

approved