137438953475domain: NAppears in sequencesa(n) = 2*4^n + 3.at n=18A1881612^p + 3 where p is prime.at n=11A241573a(n) = n + 1 when n <= 3, otherwise a(n) = 2^(n-2) + 3; also iterates of A005187 starting from a(1) = 2.at n=38A256994