Greatest divisor d of n! such that d=m^k with k>1.

Terms

a(0) =1a(1) =1a(2) =1a(3) =1a(4) =8a(5) =8a(6) =144a(7) =144a(8) =576a(9) =5184a(10) =518400a(11) =518400a(12) =2073600a(13) =2073600a(14) =101606400a(15) =914457600a(16) =14631321600a(17) =14631321600a(18) =526727577600a(19) =526727577600