A241403 Numbers n such that (n^2 + 2)/3 is not prime.

0, 1, 3, 4, 5, 6, 8, 9, 10, 12, 13, 14, 15, 16, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 30, 31, 32, 33, 34, 36, 38, 39, 40, 41, 42, 44, 45, 46, 47, 48, 49, 50, 51, 52, 54, 56, 57, 58, 59, 60, 61, 62, 63, 64, 66, 67, 68, 69, 70, 71, 72, 74, 75, 76, 77, 78, 80, 81, 82, 84

Offset

1,3

Links

Vincenzo Librandi, Table of n, a(n) for n = 1..9000

Example

4 is in the sequence because (4^2+2)/3 = 2*3.

Mathematica

Select[Range[0, 200], ! PrimeQ[(#^2 + 2)/3] &]

Prog

(Magma) [0, 1, 3] cat [ n: n in [2..90] | not IsPrime((n^2+2) div 3) ];

Crossrefs

Complement of A240878.

Sequence in context: A039132 A187970 A122488 * A287727 A298606 A039095

Adjacent sequences: A241400 A241401 A241402 * A241404 A241405 A241406

Keyword

nonn,easy

Author

Vincenzo Librandi, Apr 21 2014

Status

approved