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 A208132 #43 Oct 16 2012 17:07:01 %S A208132 2,4,17,15,10,26,12,19,112,34,163,91,101,135,303,97,54,229,459,70,679, %T A208132 1075,340,1041,550,836,1308,2780,606,875,4057,2398,772,1891,1065,3900, %U A208132 2610,8065,7476,4161,6023,5815,1481,351,5385,16978,3410,19756,16044,3309 %N A208132 Smallest k such that the number of composites of the form a^2 + 1 between two successive primes of this form equals 2n-1. %C A208132 Smallest k such that A206400(k) = 2n-1. %e A208132 a(4) = 15 because A206400(15) = 7 = 2*4 - 1. There are 7 composites of the form a^2+ 1 between the two primes 66^2+1 = 4357 and 74^2+1 = 5477. %p A208132 n0:=500000:T:=array(1..n0):j:=0:i:=0:for m from 2 to n0 do:x:=m^2+1:if type (x, prime)=true then j:=j+1:T[j]:=i:i:=0:else i:=i+1:fi:od: for n from 1 to 50 do:ii:=0:for k from 1 to j while(ii=0) do:if T[k]=2*n-1 then ii:=1: printf(`%d, `,k):else fi:od:od: %Y A208132 Cf. A002496, A206400. %K A208132 nonn %O A208132 1,1 %A A208132 _Michel Lagneau_, Oct 15 2012