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%I #14 May 31 2019 03:13:48
%S 1,4,33,309,2805,25566,230989,2106529,19303539,177948527,1649241049,
%T 15360074924,143682925080
%N Number of consecutive runs of 2 odd nonprimes congruent to 1 mod 4 below 10^n.
%F 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 1 mod 4 occur before interruption of a nonprime congruent to 3 mod 4.
%e a(3)=33 because 33 nonprime runs of 2 occur below 10^3, each run interrupted by a nonprime congruent to 3 mod 4
%t A091113 = Select[4 Range[0, 10^4] + 1, ! PrimeQ[#] &];
%t A091236 = Join[{0}, Select[4 Range[0, 10^4] + 3, ! PrimeQ[#] &]];
%t lst = {}; Do[If[Length[s = Select[A091113, Between[{A091236[[i]], A091236[[i + 1]]}]]] == 2, AppendTo[lst, Last[s]]], {i, Length[A091236] - 1}]; Table[Count[lst, x_ /; x < 10^n], {n, 4}] (* _Robert Price_, May 30 2019 *)
%Y Cf. A093183 A093184 A093186 A093187 A093187 A093188 A093397 A093398 A093399 A092639.
%K nonn,more
%O 1,2
%A _Enoch Haga_, Mar 30 2004
%E a(9)-a(13) from _Bert Dobbelaere_, Dec 19 2018
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