Number of degree-n even permutations of order dividing 4.

Terms

a(0) =1a(1) =1a(2) =1a(3) =1a(4) =4a(5) =16a(6) =136a(7) =736a(8) =4096a(9) =20224a(10) =99856a(11) =475696a(12) =3889216a(13) =31778176a(14) =313696384a(15) =2709911296a(16) =23006784256a(17) =179965340416