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 A093186 #14 May 31 2019 03:13:37
%S A093186 0,4,36,307,2848,25651,231031,2106565,19307362,177948719,1649246163,
%T A093186 15360077721,143683073300
%N A093186 Number of consecutive runs of 2 odd nonprimes congruent to 3 mod 4 below 10^n.
%F A093186 Generate the odd nonprime sequence with nonprimes labeled 1 mod 4 or 3 mod 4. Add count of nonprimes to sequence if 2 nonprimes congruent to 3 mod 4 occur before interruption of a nonprime congruent to 1 mod 4
%e A093186 a(3)=36 because 36 nonprime runs of 2 occur below 10^3, each run interrupted by a nonprime congruent to 1 mod 4.
%t A093186 A091113 = Select[4 Range[0, 10^4] + 1, ! PrimeQ[#] &];
%t A093186 A091236 = Select[4 Range[0, 10^4] + 3, ! PrimeQ[#] &];
%t A093186 lst = {}; Do[If[Length[s = Select[A091236, Between[{A091113[[i]], A091113[[i + 1]]}]]] == 2, AppendTo[lst, Last[s]]], {i, Length[A091113] - 1}]; Table[Count[lst, x_ /; x < 10^n], {n, 4}] (* _Robert Price_, May 30 2019 *)
%Y A093186 Cf. A093183 A093184 A093185 A093187 A093188 A093397 A093398 A093399 A092640.
%K A093186 nonn,more
%O A093186 1,2
%A A093186 _Enoch Haga_, Mar 30 2004
%E A093186 a(9)-a(13) from _Bert Dobbelaere_, Dec 19 2018