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 A028261 #13 Dec 15 2015 08:27:04 %S A028261 2,3,4,5,6,7,8,9,10,11,12,13,14,15,17,18,19,20,21,22,23,25,26,27,28, %T A028261 29,30,31,32,33,34,35,37,38,39,41,42,43,44,45,46,47,48,49,50,51,52,53, %U A028261 55,57,58,59,61,62,63,64,65,66,67,68,69,70,71,72,73,74 %N A028261 Numbers whose total number of prime factors (counting multiplicity) is squarefree. %C A028261 The complement is 1, 16, 24, 36, 40, 54, 56, 60, 81, 84, 88, 90, 100.. and contains all entries of A014613, all of A046310, all of A046312 etc. - _R. J. Mathar_, Dec 15 2015 %o A028261 (PARI) isok(n) = issquarefree(bigomega(n)); \\ _Michel Marcus_, Aug 31 2013 %Y A028261 Cf. A001222, A005117. %K A028261 nonn %O A028261 1,1 %A A028261 Daniel Asimov (dan(AT)research.att.com)