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

 

Logo

Annual appeal: Please make a donation to keep the OEIS running! Over 6000 articles have referenced us, often saying "we discovered this result with the help of the OEIS".
Other ways to donate

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A153308 Numbers n such that 10*n+7 is not prime. 1
2, 5, 7, 8, 11, 14, 17, 18, 20, 21, 23, 24, 26, 28, 29, 32, 35, 37, 38, 40, 41, 42, 43, 44, 47, 49, 50, 51, 52, 53, 56, 59, 62, 63, 65, 66, 68, 69, 70, 71, 73, 74, 76, 77, 80, 81, 83, 84, 86, 89, 91, 92, 95, 98, 100, 101, 102, 103, 104, 105, 106, 107 (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 terms in the following triangular array:

*;

*,*;

*,*,*;

2,*,*,*;

*,*,7,*,*;

*,*,*,11,*,*;

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

*,*,*,*,18,*,*,*;

5,*,*,*,*,24,*,*,*;

*,*,14,*,*,*,*,35,*,*;

*,*,*,20,*,*,*,*,43,*,*;etc.

where * marks the non-integer values of (2*h*k + k + h - 3)/5 with h >= k >= 1. - Vincenzo Librandi, Jan 17 2013

MATHEMATICA

Select[Range[0, 200], !PrimeQ[10*# + 7]&] (* Vincenzo Librandi, Jan 12 2013 *)

PROG

(MAGMA) [n: n in [0..150] | not IsPrime(10*n + 7)]; // Vincenzo Librandi, Jan 12 2013

CROSSREFS

A102342.

Sequence in context: A138671 A286693 A032724 * A216565 A285938 A192111

Adjacent sequences:  A153305 A153306 A153307 * A153309 A153310 A153311

KEYWORD

nonn,easy

AUTHOR

Vincenzo Librandi, Dec 23 2008

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 November 19 03:53 EST 2017. Contains 294912 sequences.