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 A236627 #17 Mar 15 2018 04:35:58 %S A236627 0,0,0,0,1,0,1,0,1,1,2,0,2,1,1,1,3,1,3,1,2,2,3,0,3,3,3,2,4,1,4,2,3,3, %T A236627 3,1,5,4,4,2,5,2,5,3,3,4,5,1,5,4,5,4,6,3,5,3,5,5,6,1,6,5,4,4,6,4,7,5, %U A236627 6,4,7,2,7,6,5,5,6,4,7,3,6,7,8,3,7,7,7,5,8,3,7,6,7,7,7,3,8,6,6,5,9 %N A236627 Number of positive integers <= sqrt(n) not dividing n. %C A236627 It appears that the indices of the zeros in the sequence are in A018253. %H A236627 Omar E. Pol, , <a href="http://www.polprimos.com/imagenespub/poldiv13.jpg">Three illustrations of A000005 giving the structure of this sequence</a>, (2013) %F A236627 a(n) = A000196(n) - A038548(n) = A160812(n)/2. %o A236627 (PARI) a(n) = sum(i=1, sqrtint(n), (n % i) != 0); \\ _Michel Marcus_, Mar 16 2014 %Y A236627 Cf. A000005, A000196, A010052, A018253, A038548, A007491, A160812, A161205, A212119, A228813, A228814, A229940, A229942, A229944, A229950, A229951. %K A236627 nonn %O A236627 1,11 %A A236627 _Omar E. Pol_, Feb 05 2014