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 A161867 #15 Aug 13 2025 21:27:06
%S A161867 4,8,11,5,2,7,25,29,2,35,39,21,47,2,51,28,61,64,67,35,37,79,81,83,89,
%T A161867 93,95,33,104,2,109,113,39,121,125,65,131,133,137,47,37,151,51,2,161,
%U A161867 165,2,171,179,89,177,184,191,49,201,199,101,207,208,43,109,55,227,2,233,119
%N A161867 Denominators of ratio of nonprimes in a square interval to that of nonprimes in that interval and its successor.
%H A161867 G. C. Greubel, <a href="/A161867/b161867.txt">Table of n, a(n) for n = 1..1000</a>
%F A161867 The limit of this sequence of ratios is 1/2, as can be shown by setting an increasing lower bound on the ratio of composites in successive square intervals.
%e A161867 First few ratios are 1/4, 3/8, 5/11, 2/5, 1/2, 3/7, 12/25, 13/29.
%t A161867 Denominator[Table[((2 n + 1) - (PrimePi[(n + 1)^2] - PrimePi[n^2]))/((4 n + 4) - (PrimePi[(n + 2)^2] - PrimePi[n^2])), {n, 1, 100}]] (* corrected by _G. C. Greubel_, Dec 20 2016 *)
%Y A161867 Cf. A161865, numerators for this sequence.
%K A161867 nonn,frac
%O A161867 1,1
%A A161867 _Daniel Tisdale_, Jun 20 2009
%E A161867 Keyword:frac added by _R. J. Mathar_, Jun 30 2009
%E A161867 Extended beyond a(9) by _R. J. Mathar_, Sep 27 2009