Number of degree-n permutations of order dividing 4.

Terms

a(0) =1a(1) =1a(2) =2a(3) =4a(4) =16a(5) =56a(6) =256a(7) =1072a(8) =6224a(9) =33616a(10) =218656a(11) =1326656a(12) =9893632a(13) =70186624a(14) =574017536a(15) =4454046976a(16) =40073925376a(17) =347165733632