a(n) = Product_{k=2..n-1} MultiplicativeOrder(k,n) where gcd(k,n)=1.

Terms

a(0) =1a(1) =1a(2) =2a(3) =2a(4) =32a(5) =2a(6) =648a(7) =8a(8) =648a(9) =32a(10) =12500000a(11) =8a(12) =214990848a(13) =648a(14) =2048a(15) =2048a(17) =648a(19) =2048a(20) =3359232a(21) =12500000a(23) =128a(25) =214990848