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
Examples
4 is in the sequence because (4^2+2)/3 = 2*3.
Links
- Vincenzo Librandi, Table of n, a(n) for n = 1..9000
Crossrefs
Complement of A240878.
Programs
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Magma
[0,1,3] cat [ n: n in [2..90] | not IsPrime((n^2+2) div 3) ];
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Mathematica
Select[Range[0,200], ! PrimeQ[(#^2 + 2)/3] &]