A153170 - OEIS

A153170

Numbers k such that 3*k + 2 is not prime.

2, 4, 6, 8, 10, 11, 12, 14, 16, 18, 20, 21, 22, 24, 25, 26, 28, 30, 31, 32, 34, 36, 38, 39, 40, 41, 42, 44, 46, 47, 48, 50, 51, 52, 53, 54, 56, 58, 60, 61, 62, 64, 66, 67, 68, 69, 70, 71, 72, 73, 74, 76, 78, 80, 81, 82, 84, 86, 88, 90, 91, 92, 94, 95, 96, 98, 99, 100, 101, 102

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OFFSET

1,1

COMMENTS

Contains the positive even numbers (A005843) and the odd numbers of the form 2*A059324(.) + 1. - R. J. Mathar, Nov 27 2010

Numbers k such that (3*k)!/(3*k + 2) is an integer. - Peter Bala, Jan 25 2017

LINKS

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

EXAMPLE

Distribution of the odd terms in the following triangular array:

*, *;

*, 11, *;

*, *, *, *;

*, *, 25, *, *;

*, 21, *, *, 47, *;

*, *, *, *, *, *, *;

*, *, 39, *, *, 73, *, *;

*, 31, *, *, 69, *, *, 107, *;

*, *, *, *, *, *, *, *, *, *;

*, *, 53, *, *, 99, *, *, 145, *, *;

*, 41, *, *, 91, *, *, 141, *, *, 191, *;

etc., where * marks the noninteger values of (4*h*k + 2*k + 2*h - 1)/3 with h >= k >= 1. - Vincenzo Librandi, Jan 15 2013

MAPLE

for n from 0 to 100 do

if irem(factorial(3*n), 3*n+2) = 0 then print(n); end if;

end do: # Peter Bala, Jan 25 2017

MATHEMATICA

Select[Range[1, 200], !PrimeQ[3*# + 2] &] (* Vincenzo Librandi, Oct 11 2012 *)

PROG

(PARI) for(n=1, 200, if(!isprime(3*n+2), print1(n, ", "))) \\ Joerg Arndt, Nov 27 2010

(Magma) [n: n in [1..110] | not IsPrime(3*n + 2)]; // Vincenzo Librandi, Oct 11 2012

CROSSREFS

Cf. A024893, A014076, A045751, A095277, A153088, A153329, A153343.

Sequence in context: A176995 A225793 A154809 * A067030 A072427 A337430

Adjacent sequences: A153167 A153168 A153169 * A153171 A153172 A153173

KEYWORD

nonn,easy

AUTHOR

Vincenzo Librandi, Dec 20 2008

EXTENSIONS

Edited by N. J. A. Sloane, Jun 23 2010

STATUS

approved