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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 non-integer 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

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Last modified November 18 10:38 EST 2017. Contains 294887 sequences.