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 A159973 #6 Aug 31 2023 17:57:49 %S A159973 3,4,5,6,7,10,11,13,14,15,16,17,19,20,21,22,23,25,26,27,28,29,30,31, %T A159973 32,33,34,35,37,38,39,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,57, %U A159973 58,59,61,62,63,64,65,66,67,68,69,70,71,73,74,75,76,77,78,79,81,82,83,85 %N A159973 Non-refactorable numbers: number of divisors of n does not divide n. %t A159973 Select[Range[100],Mod[#,DivisorSigma[0,#]]!=0&] (* _Harvey P. Dale_, Aug 31 2023 *) %o A159973 (Magma) [ n: n in [1..85] | n mod #Divisors(n) ne 0 ]; %Y A159973 Complement of A033950. %K A159973 nonn %O A159973 1,1 %A A159973 _Jaroslav Krizek_, Apr 28 2009 %E A159973 Edited and extended by _Klaus Brockhaus_, Apr 29 2009