%I #17 Apr 17 2013 04:18:31

%S 3,4,2,20,60,92,246,752,1289,2084,3383

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

%e In A210487, 2 appears for the first time as A210487(3), so a(1)=3;

%e 3 appears for the first time as A210487(4), so a(2)=4;

%e 5 appears for the first time as A210487(2), so a(3)=2.

%p N := 60 ;

%p A210488 := [seq(0,i=1..N)] ;

%p for n from 2 do

%p a := A210487(n) ;

%p if isprime(a) then

%p idx := numtheory[pi](a) ;

%p if idx <= N then

%p if op(idx,A210488) = 0 then

%p A210488 := subsop(idx=n,A210488) ;

%p print(A210488) ;

%p end if;

%p end if;

%p end if;

%p end do: # _R. J. Mathar_, Apr 17 2013

%t 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 Cf. A000040, A210487, A147971.

%K nonn,hard

%O 1,1

%A _Lei Zhou_, Jan 23 2013