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A153275 Numbers n such that 10*n+1 is not prime. 3
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
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
MAPLE
q:= n-> not isprime(10*n+1):
select(q, [$0..120])[]; # Alois P. Heinz, Jan 21 2021
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
Sequence in context: A062803 A231756 A212591 * A362310 A161154 A174438
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 March 29 10:59 EDT 2024. Contains 371277 sequences. (Running on oeis4.)