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 A153275 Numbers n such that 10*n+1 is not prime. 2
 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 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 Cf. A024912, A053178, A153329. 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 May 6 03:25 EDT 2021. Contains 343580 sequences. (Running on oeis4.)