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 A153329 Numbers k such that 5*k + 1 is not prime. 7
 0, 1, 3, 4, 5, 7, 9, 10, 11, 13, 15, 16, 17, 18, 19, 21, 22, 23, 24, 25, 27, 28, 29, 31, 32, 33, 34, 35, 37, 39, 40, 41, 43, 44, 45, 46, 47, 49, 51, 52, 53, 55, 57, 58, 59, 60, 61, 63, 64, 65, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 81, 82, 83, 85, 87 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 COMMENTS Numbers k such that (5*k)!/(5*k + 1) is an integer. - Peter Bala, Jan 25 2017 LINKS Vincenzo Librandi, Table of n, a(n) for n = 1..1000 EXAMPLE Distribution of the even terms in the following triangular array: *; *, *; 4, *, *; *, *, *, 16; *, *, *, *, 24; *, *, 18, *, *, *; *, *, *, *, *, *, *; 10, *, *, *, *, 44, *, *; *, *, *, 34, *, *, *, *, 72; *, *, *, *, 46, *, *, *, *, 88; *, *, 32, *, *, *, *, 78, *, *, *; etc., where * marks the noninteger values of (4*h*k + 2*k + 2*h)/5 with h >= k >= 1. - Vincenzo Librandi, Jan 17 2013 MAPLE for n from 0 to 100 do if irem(factorial(5*n), 5*n+1) = 0 then print(n); end if; end do: # Peter Bala, Jan 25 2017 MATHEMATICA Select[Range[0, 200], !PrimeQ[5*# + 1]&] (* Vincenzo Librandi, Jan 12 2013 *) PROG (Magma) [n: n in [0..150] | not IsPrime(5*n + 1)]; // Vincenzo Librandi, Jan 12 2013 CROSSREFS Cf. A024894, A014076, A153170, A045751, A095277, A153088, A153343. Sequence in context: A335002 A276155 A273670 * A213637 A047251 A258932 Adjacent sequences: A153326 A153327 A153328 * A153330 A153331 A153332 KEYWORD nonn,easy AUTHOR Vincenzo Librandi, Dec 23 2008 EXTENSIONS Erroneous comment deleted by N. J. A. Sloane, Jun 23 2010 0 added by Arkadiusz Wesolowski, Aug 03 2011 STATUS approved

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Last modified May 29 14:43 EDT 2024. Contains 372952 sequences. (Running on oeis4.)