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A153275 Numbers n such that 10*n+1 is not prime.

%I A153275 #27 Sep 08 2022 08:45:39
%S A153275 0,2,5,8,9,11,12,14,16,17,20,22,23,26,29,30,32,34,35,36,37,38,39,41,
%T A153275 44,45,47,48,50,51,53,55,56,58,59,61,62,65,67,68,71,72,73,74,77,78,79,
%U A153275 80,83,84,85,86,87,89,90,92,93,95,96,98,100,101,104,107,108,110
%N A153275 Numbers n such that 10*n+1 is not prime.
%C A153275 Multiplied by 2 we have 4,10,16,18,... which is the set of even terms of A153329. - _R. J. Mathar_, Jan 23 2009
%H A153275 Vincenzo Librandi, <a href="/A153275/b153275.txt">Table of n, a(n) for n = 1..1000</a>
%F A153275 a(n) = (A053178(n)-1)/10. - _R. J. Mathar_, Oct 30 2009
%e A153275 Distribution of the terms in the following triangular array:
%e A153275 *;
%e A153275 *,*;
%e A153275 2,*,*;
%e A153275 *,*,*,8;
%e A153275 *,*,*,*,12;
%e A153275 *,*,9,*,*,*;
%e A153275 *,*,*,*,*,*,*;
%e A153275 5,*,*,*,*,22,*,*;
%e A153275 *,*,*,17,*,*,*,*,36;
%e A153275 *,*,*,*,23,*,*,*,*,44;
%e A153275 *,*,16,*,*,*,*,39,*,*,*; etc.
%e A153275 where * marks the non-integer values of (2*h*k + k + h)/5 with h >= k >= 1. - _Vincenzo Librandi_, Jan 15 2013
%p A153275 q:= n-> not isprime(10*n+1):
%p A153275 select(q, [$0..120])[];  # _Alois P. Heinz_, Jan 21 2021
%t A153275 Select[Range[0, 200], !PrimeQ[10*# + 1]&] (* _Vincenzo Librandi_, Jan 12 2013 *)
%o A153275 (Magma) [n: n in [0..150] | not IsPrime(10*n + 1)]; // _Vincenzo Librandi_, Jan 12 2013
%Y A153275 Cf. A024912, A053178, A153329.
%K A153275 nonn,easy
%O A153275 1,2
%A A153275 _Vincenzo Librandi_, Dec 22 2008
%E A153275 63 replaced by 53 by _R. J. Mathar_, Jan 23 2009
%E A153275 0 added by _Arkadiusz Wesolowski_, Aug 03 2011