# Greetings from The On-Line Encyclopedia of Integer Sequences! http://oeis.org/ Search: id:a153088 Showing 1-1 of 1 %I A153088 #23 Sep 08 2022 08:45:39 %S A153088 1,2,3,5,7,8,9,10,11,13,14,15,17,19,20,21,23,24,25,26,27,29,31,32,33, %T A153088 34,35,37,38,39,41,42,43,44,45,47,49,50,51,52,53,55,56,57,58,59,60,61, %U A153088 62,63,64,65,66,67,68,69,71,73,74,75,77,79,80,81,83,85,86,87,89,91,92,93 %N A153088 Numbers k such that 5*k - 1 is not prime. %H A153088 Vincenzo Librandi, Table of n, a(n) for n = 1..1000 %F A153088 a(n) = A153343(n) + 1. - _Peter Bala_, Jan 25 2017 %e A153088 Distribution of the even terms in the following triangular array: %e A153088 2; %e A153088 *, *; %e A153088 *, *, 10; %e A153088 *, *, *, *; %e A153088 *, *, *, 20, *; %e A153088 8, *, *, *, *, 34; %e A153088 *, *, *, *, *, *, *; %e A153088 *, *, 24, *, *, *, *, 58; %e A153088 *, *, *, *, 42, *, *, *, *; %e A153088 *, *, *, 38, *, *, *, *, 80, *; %e A153088 14, *, *, *, *, 60, *, *, *, *, 106; %e A153088 etc., where * marks the noninteger values of (4*h*k + 2*k + 2*h + 2)/5 with h >= k >= 1. - _Vincenzo Librandi_, Jan 15 2013 %p A153088 # produces the sequence apart from the initial terms 1 and 2 %p A153088 for n from 0 to 100 do %p A153088 if irem(factorial(5*n), 5*n+4) = 0 then print(n+1); end if; %p A153088 end do: # _Peter Bala_, Jan 25 2017 %t A153088 Select[Range[1, 200], !PrimeQ[5 # - 1] &] (* _Vincenzo Librandi_, Oct 11 2012 *) %o A153088 (Magma) [n: n in [1..100] | not IsPrime(5*n-1)]; // _Vincenzo Librandi_, Oct 11 2012 %Y A153088 Cf. A153355, A014076, A153170, A045751, A095277, A153329, A153343. %K A153088 nonn,easy %O A153088 1,2 %A A153088 _Vincenzo Librandi_, Jan 03 2009 %E A153088 First 29 replaced with 20, 4 replaced with 44, extended by _R. J. Mathar_, Jan 05 2009 %E A153088 Erroneous comment deleted by _N. J. A. Sloane_, Jun 23 2010 # Content is available under The OEIS End-User License Agreement: http://oeis.org/LICENSE