255250280182domain: NAppears in sequencesa(n) is the smallest base of the form 2 + 10*k which is characterized by a convergence speed of n, where A317905(n) represents the convergence speed of m^^m.at n=15A340345a(n) is the smallest positive k such that k^2 + 1 has 2*n divisors, or -1 if no such k exists.at n=16A353008