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 A210488 a(n) is the index of A210487 when the n-th prime appears for the first time. 1
 3, 4, 2, 20, 60, 92, 246, 752, 1289, 2084, 3383 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS EXAMPLE In A210487, 2 appears for the first time as A210487(3), so a(1)=3; 3 appears for the first time as A210487(4), so a(2)=4; 5 appears for the first time as A210487(2), so a(3)=2. MAPLE N := 60 ; A210488 := [seq(0, i=1..N)] ; for n from 2 do     a := A210487(n) ;     if isprime(a) then         idx := numtheory[pi](a) ;         if idx <= N then         if op(idx, A210488) = 0 then             A210488  := subsop(idx=n, A210488) ;             print(A210488) ;         end if;         end if;     end if; end do: # R. J. Mathar, Apr 17 2013 MATHEMATICA 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 CROSSREFS Cf. A000040, A210487, A147971. Sequence in context: A166074 A225475 A259334 * A244364 A218610 A260958 Adjacent sequences:  A210485 A210486 A210487 * A210489 A210490 A210491 KEYWORD nonn,hard AUTHOR Lei Zhou, Jan 23 2013 STATUS approved

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Last modified August 20 21:29 EDT 2019. Contains 326155 sequences. (Running on oeis4.)