a(n) = (largest prime < 10^n) + (smallest prime > 10^n).

A097515

a(n) = (largest prime < 10^n) + (smallest prime > 10^n).

Terms

    a(0) =18a(1) =198a(2) =2006a(3) =19980a(4) =199994a(5) =1999986a(6) =20000010a(7) =199999996a(8) =1999999944a(9) =19999999986a(10) =199999999980

External references