Smaller central (median) divisor of n!.

Terms

a(0) =1a(1) =1a(2) =2a(3) =4a(4) =10a(5) =24a(6) =70a(7) =192a(8) =576a(9) =1890a(10) =6300a(11) =21600a(12) =78848a(13) =294840a(14) =1143072a(15) =4572288a(16) =18849600a(17) =79968000a(18) =348566400a(19) =1559376000a(20) =7147140000a(21) =33522128640a(22) =160758097500a(23) =787652812800