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

Author

Vincenzo Librandi, Apr 20 2014

Keywords

• nonn
• easy

Examples

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

Links

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

Crossrefs

Complement of A155736.

Programs

Magma

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

Mathematica

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