A153403 Numbers n such that 10*n+3 is not prime.

3, 6, 9, 12, 13, 14, 15, 18, 20, 21, 24, 25, 27, 30, 32, 33, 34, 36, 39, 40, 41, 42, 45, 47, 48, 49, 51, 53, 54, 55, 57, 58, 60, 62, 63, 66, 69, 70, 71, 72, 75, 76, 78, 79, 80, 81, 83, 84, 87, 89, 90, 91, 92, 93, 94, 96, 97, 99, 100

Offset: 1

Author

Vincenzo Librandi, Dec 25 2008

Keywords

• nonn
• easy

Examples

			Distribution of the terms in the following triangular array:
*;
*,*;
*,*,*;
*,*,6,*;
3,*,*,*,*;
*,*,*,*,14,*;
*,*,*,*,*,*,*;
*,*,*,15,*,*,*,*;
*,*,13,*,*,*,*,32,*;
6,*,*,*,*,27,*,*,*,*;
*,*,*,*,25,*,*,*,*,48,*; etc.
where * marks the non-integer values of (2*h*k + k + h - 1)/5 with n >= k >= 1. - _Vincenzo Librandi_, Jan 14 2013
		

Links

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

Crossrefs

Cf. A102338.

Programs

Magma

[n: n in [0..150] | not IsPrime(10*n + 3)]; // Vincenzo Librandi, Jan 14 2013

Mathematica

lst={};Do[p=10*n+3;If[ !PrimeQ[p],AppendTo[lst,n]],{n,0,6!}];lst (* Vladimir Joseph Stephan Orlovsky, May 12 2010 *)
Select[Range[100],CompositeQ[10#+3]&] (* Harvey P. Dale, Jan 19 2025 *)