

A153275


Numbers n such that 10*n+1 is not prime.


1



0, 2, 5, 8, 9, 11, 12, 14, 16, 17, 20, 22, 23, 26, 29, 30, 32, 34, 35, 36, 37, 38, 39, 41, 44, 45, 47, 48, 50, 51, 53, 55, 56, 58, 59, 61, 62, 65, 67, 68, 71, 72, 73, 74, 77, 78, 79, 80, 83, 84, 85, 86, 87, 89, 90, 92, 93, 95, 96, 98, 100, 101, 104, 107, 108, 110
(list;
graph;
refs;
listen;
history;
text;
internal format)



OFFSET

1,2


COMMENTS

Multiplied by 2 we have 4,10,16,18,... which is the set of even terms of A153329.  R. J. Mathar, Jan 23 2009


LINKS

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


FORMULA

a(n) = (A053178(n)1)/10. [R. J. Mathar, Oct 30 2009]


EXAMPLE

Distribution of the terms in the following triangular array:
*;
*,*;
2,*,*;
*,*,*,8;
*,*,*,*,12;
*,*,9,*,*,*;
*,*,*,*,*,*,*;
5,*,*,*,*,22,*,*;
*,*,*,17,*,*,*,*,36;
*,*,*,*,23,*,*,*,*,44;
*,*,16,*,*,*,*,39,*,*,*; etc.
where * marks the noninteger values of (2*h*k + k + h)/5 with h >= k >= 1.  Vincenzo Librandi, Jan 15 2013


MATHEMATICA

Select[Range[0, 200], !PrimeQ[10*# + 1]&] (* Vincenzo Librandi, Jan 12 2013 *)


PROG

(MAGMA) [n: n in [0..150]  not IsPrime(10*n + 1)]; // Vincenzo Librandi, Jan 12 2013


CROSSREFS

Cf. A024912.
Sequence in context: A062803 A231756 A212591 * A161154 A174438 A176061
Adjacent sequences: A153272 A153273 A153274 * A153276 A153277 A153278


KEYWORD

nonn,easy


AUTHOR

Vincenzo Librandi, Dec 22 2008


EXTENSIONS

63 replaced by 53 by R. J. Mathar, Jan 23 2009
0 added by Arkadiusz Wesolowski, Aug 03 2011


STATUS

approved



