This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A153040 #32 Dec 05 2024 11:39:56 %S A153040 7,10,13,15,16,19,20,22,25,27,28,30,31,34,35,37,40,41,43,45,46,48,49, %T A153040 50,52,55,58,60,61,62,63,64,65,67,69,70,73,74,75,76,79,80,82,83,85,87, %U A153040 88,90,91,94,95,96,97,100,103,104,105,106,107,109,110,111 %N A153040 Numbers n>3 such that 2*n-5 is not a prime. %C A153040 One less than the associated number in A153039; one more than that in A153043. - _R. J. Mathar_ Dec 20 2008 %H A153040 Vincenzo Librandi, <a href="/A153040/b153040.txt">Table of n, a(n) for n = 1..1000</a> %F A153040 Let p = prime number n = (p^2+5)/2 mod (p) %t A153040 Select[Range[4,200],!PrimeQ[2*#-5]&] (* _Vladimir Joseph Stephan Orlovsky_, Feb 09 2012 *) %o A153040 (Magma) [n: n in [4..120]|not IsPrime(2*n-5)]; // _Vincenzo Librandi_, Aug 30 2012 %Y A153040 Cf. A089253, A153039. %K A153040 nonn,easy %O A153040 1,1 %A A153040 _Vincenzo Librandi_, Dec 17 2008 %E A153040 Flipped sign in definition. - _R. J. Mathar_, Dec 20 2008