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

1,2

Links

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

Example

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

Mathematica

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

Prog

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

Crossrefs

Cf. A111094.

Sequence in context: A115888 A143814 A088971 * A289076 A372519 A342779

Adjacent sequences: A153397 A153398 A153399 * A153401 A153402 A153403

Keyword

nonn,easy

Author

Vincenzo Librandi, Dec 25 2008

Extensions

0 added by Arkadiusz Wesolowski, Aug 03 2011

Status

approved