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A153170 Numbers k such that 3*k + 2 is not prime. 8
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 (list; graph; refs; listen; history; text; internal format)
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

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Last modified December 9 17:01 EST 2022. Contains 358701 sequences. (Running on oeis4.)