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A153347 Numbers n>0 such that 7*n-4 is not prime. 1
2, 4, 6, 7, 8, 10, 12, 13, 14, 16, 17, 18, 19, 20, 21, 22, 24, 25, 26, 27, 28, 30, 31, 32, 34, 36, 37, 38, 40, 42, 43, 44, 46, 47, 48, 49, 50, 52, 54, 55, 56, 57, 58, 60, 61, 62, 63, 64, 65, 66, 67, 68, 70, 71, 72, 73, 74, 76, 77, 78, 79, 80, 82, 84, 85, 86, 87, 88, 90, 91, 92 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

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

EXAMPLE

Distribution of the odd terms in the following triangular array:

*;

*,*;

*,*,*;

*,7,*,*;

*,*,*,*,*;

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

7,*,*,*,*,*,*;

*,*,*,*,*,*,37,*;

*,*,*,25,*,*,*,*,*;

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

*,17,*,*,*,*,*,*,63,*,*;

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

*,*,*,*,43,*,*,*,*,*,*,97,*;

13,*,*,*,*,*,*,71,*,*,*,*,*,*; etc.

where * marks the non-integer values of (4*h*k + 2*k + 2*h + 5)/7 with h >= k >= 1. - Vincenzo Librandi, Jan 17 2013

MATHEMATICA

Select[Range[1, 200], !PrimeQ[7 # - 4]&] (* Vincenzo Librandi, Jan 13 2013 *)

PROG

(MAGMA) [n: n in [1..150] | not IsPrime(7*n-4)]; // Vincenzo Librandi, Jan 13 2013

CROSSREFS

Cf. A024903.

Sequence in context: A138204 A080645 A024413 * A153167 A227187 A047237

Adjacent sequences:  A153344 A153345 A153346 * A153348 A153349 A153350

KEYWORD

nonn,easy

AUTHOR

Vincenzo Librandi, Dec 24 2008

EXTENSIONS

Erroneous comment deleted by N. J. A. Sloane, Jun 23 2010

STATUS

approved

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Last modified June 17 19:10 EDT 2019. Contains 324198 sequences. (Running on oeis4.)