

A181766


Numbers n such that 3*n + 7 is not prime.


1



1, 3, 5, 6, 7, 9, 11, 13, 14, 15, 16, 17, 19, 21, 23, 25, 26, 27, 28, 29, 31, 33, 35, 36, 37, 38, 39, 41, 42, 43, 45, 46, 47, 49, 51, 53, 54, 55, 56, 57, 59, 60, 61, 63, 65, 66, 67, 69, 70, 71, 73, 75, 76, 77, 79, 80, 81, 82, 83, 84, 85, 86, 87, 89, 91, 93, 94, 95, 96, 97, 98
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OFFSET

1,2


COMMENTS

One less than the associated value in A153282, two less than A153309.  R. J. Mathar, Jan 05 2011


LINKS

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


EXAMPLE

Distribution of the even terms in the following triangular array:
*;
*, 6;
*, *,14;
*, *,*,*;
*,16,*,*,38;
*,*,28,*,*,54;
*,*, *,*,*, *,*;
*,26,*,*,60,*,*,94;
*,*,42,*,*,80,*,*,118;
*,*,*, *,*,*, *,*, *, *;
*,36,*,*,82,*,*,128,*,*,174;
*,*,56,*,*,106,*,*,156,*,*,206; etc.
where * marks the noninteger values of (4*h*k + 2*k + 2*h  6)/3 with h >= k >= 1.  Vincenzo Librandi, Jan 15 2013


MATHEMATICA

Select[Range[0, 100], !PrimeQ[3 # + 7] &] (* Vincenzo Librandi, Oct 15 2012 *)


PROG

(MAGMA) [n: n in [0..100]  not IsPrime(3*n + 7)]; // Vincenzo Librandi, Oct 15 2012


CROSSREFS

Cf. A089953 (3*n+7 is a prime).
Sequence in context: A285627 A064802 A233570 * A047584 A229089 A277573
Adjacent sequences: A181763 A181764 A181765 * A181767 A181768 A181769


KEYWORD

nonn,easy


AUTHOR

Vincenzo Librandi


STATUS

approved



