A153380 Numbers n such that 10*n+9 is not prime.

0, 3, 4, 6, 9, 11, 12, 15, 16, 18, 20, 21, 24, 25, 27, 28, 29, 30, 31, 32, 33, 36, 39, 42, 45, 46, 48, 51, 52, 53, 54, 55, 57, 58, 60, 62, 63, 64, 66, 67, 68, 69, 72, 74, 75, 77, 78, 79, 81, 84, 86, 87, 88, 89, 90, 93, 94, 95, 96, 97, 98, 99, 102

Offset: 1

Author

Vincenzo Librandi, Dec 25 2008

Keywords

• nonn
• easy

Examples

			Triangle begins:
0;
*,*;
*,*,4;
*,*,*,*;
*,*,*,*,*;
3,*,*,*,*,16;
*,*,*,*,*,*,*;
*,*,11,*,*,*,*,28;
*,*,*,*,20,*,*,*,*;
*,*,*,*,*,*,*,*,*,*;
6,*,*,*,*,29,*,*,*,*,52;
where * marks the non-integer values of (2*h*k + k + h - 4)/5 with h >= k >= 1. - _Vincenzo Librandi_, Jan 13 2013
		

Links

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

Crossrefs

Cf. A102700.

Programs

Magma

[n: n in [0..150] | not IsPrime(10*n+9)]; // Vincenzo Librandi, Jan 13 2013

Mathematica

Select[Range[0, 200], !PrimeQ[10 # + 9] &] (* Vincenzo Librandi, Jan 13 2013 *)

Extensions

0 added by Arkadiusz Wesolowski, Aug 03 2011