login
This site is supported by donations to The OEIS Foundation.

 

Logo

The OEIS is looking to hire part-time people to help edit core sequences, upload scanned documents, process citations, fix broken links, etc. - Neil Sloane, njasloane@gmail.com

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
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 (list; graph; refs; listen; history; text; internal format)
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 non-integer 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

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent | More pages
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy .

Last modified May 27 13:30 EDT 2017. Contains 287205 sequences.