A241266 Numbers n such that 4*n^2+2*n-1 is not prime.

6, 7, 9, 11, 16, 17, 18, 20, 21, 26, 29, 31, 36, 37, 39, 40, 41, 42, 44, 45, 46, 49, 51, 52, 53, 54, 55, 56, 58, 59, 61, 62, 64, 66, 68, 71, 73, 75, 76, 78, 81, 83, 84, 85, 86, 89, 91, 95, 96, 97, 99, 100, 101, 102, 104, 105, 106, 107, 108, 111, 112, 113, 114

Offset

1,1

Links

Vincenzo Librandi, Table of n, a(n) for n = 1..1000

Example

7 is in this sequence because 4*7^2+2*7-1 = 209 = 11*19.

Mathematica

Select[Range[200], ! PrimeQ[4 #^2 + 2 # - 1] &]

Prog

(Magma) [n: n in [1..150] |not IsPrime(4*n^2+2*n-1)];

Crossrefs

Complement of A155736.

Sequence in context: A094010 A100348 A240882 * A095908 A094698 A361419

Adjacent sequences: A241263 A241264 A241265 * A241267 A241268 A241269

Keyword

nonn,easy

Author

Vincenzo Librandi, Apr 20 2014

Status

approved