Product of prime powers <= n.

Terms

a(0) =1a(1) =1a(2) =2a(3) =6a(4) =24a(5) =120a(6) =120a(7) =840a(8) =6720a(9) =60480a(10) =60480a(11) =665280a(12) =665280a(13) =8648640a(14) =8648640a(15) =8648640a(16) =138378240a(17) =2352430080a(18) =2352430080a(19) =44696171520a(20) =44696171520a(21) =44696171520a(22) =44696171520