a(n) = numerator( n^n/(2*n)! ).

Terms

a(0) =1a(1) =1a(2) =1a(3) =3a(4) =2a(5) =125a(6) =3a(7) =16807a(8) =512a(9) =59049a(10) =15625a(11) =2357947691a(12) =36a(14) =282475249a(15) =1171875a(16) =8589934592a(18) =1162261467a(20) =195312500a(24) =603979776