A153400 Numbers n such that 18*n+1 is not prime.

0, 3, 5, 8, 12, 13, 14, 16, 18, 19, 20, 23, 25, 26, 28, 31, 33, 36, 37, 38, 39, 40, 43, 44, 47, 48, 50, 53, 54, 57, 58, 60, 61, 63, 66, 67, 68, 69, 70, 73, 74, 75, 76, 77, 78, 80, 82, 83, 84, 88, 89, 91, 93, 95, 96, 98

Offset: 1

Author

Vincenzo Librandi, Dec 25 2008

Keywords

• nonn
• easy

Examples

			Distribution of the positive terms in the following triangular array:
*;
*,*;
*,*,*;
*,*,*,*;
*,3,*,*,*;
*,*,5,*,*,*;
*,*,*,*,*,*,*;
*,*,*,*,*,*,*,16;
*,*,*,*,*,*,*,*,20;
*,*,*,*,*,*,*,*,*,*;
*,*,*,*,14,*,*,*,*,*,*; etc.
where * marks the noninteger values of (2*h*k + k + h)/9 with h >= k >= 1. - _Vincenzo Librandi_, Jan 14 2013
		

Links

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

Crossrefs

Cf. A111094.

Programs

Magma

[n: n in [0..150] | not IsPrime(18*n+1)]; // Vincenzo Librandi, Jan 14 2013

Mathematica

Select[Range[0, 200], !PrimeQ[18 # + 1] &] (* Vincenzo Librandi, Jan 14 2013 *)

Extensions

0 added by Arkadiusz Wesolowski, Aug 03 2011