a(n) = floor(n^(n/2)).

Terms

a(0) =1a(1) =1a(2) =2a(3) =5a(4) =16a(5) =55a(6) =216a(7) =907a(8) =4096a(9) =19683a(10) =100000a(11) =534145a(12) =2985984a(13) =17403307a(14) =105413504a(15) =661735513a(16) =4294967296a(17) =28761784747a(18) =198359290368