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A210488 a(n) is the index of A210487 when the n-th prime appears for the first time.

%I A210488 #17 Apr 17 2013 04:18:31
%S A210488 3,4,2,20,60,92,246,752,1289,2084,3383
%N A210488 a(n) is the index of A210487 when the n-th prime appears for the first time.
%e A210488 In A210487, 2 appears for the first time as A210487(3), so a(1)=3;
%e A210488 3 appears for the first time as A210487(4), so a(2)=4;
%e A210488 5 appears for the first time as A210487(2), so a(3)=2.
%p A210488 N := 60 ;
%p A210488 A210488 := [seq(0,i=1..N)] ;
%p A210488 for n from 2 do
%p A210488     a := A210487(n) ;
%p A210488     if isprime(a) then
%p A210488         idx := numtheory[pi](a) ;
%p A210488         if idx <= N then
%p A210488         if op(idx,A210488) = 0 then
%p A210488             A210488  := subsop(idx=n,A210488) ;
%p A210488             print(A210488) ;
%p A210488         end if;
%p A210488         end if;
%p A210488     end if;
%p A210488 end do: # _R. J. Mathar_, Apr 17 2013
%t A210488 nn = 11; a = Table[0, {nn}]; k = 1; While[Times @@ a == 0, k++; p1 = Prime[k]; id = PrimePi[Min[Table[Last[FactorInteger[Prime[k]^2 - Prime[j]^2]][[1]], {j, k - 1}]]]; If[id <= nn && a[[id]] == 0, a[[id]] = k]]; a
%Y A210488 Cf. A000040, A210487, A147971.
%K A210488 nonn,hard
%O A210488 1,1
%A A210488 _Lei Zhou_, Jan 23 2013