Number of degree-n odd permutations of order 2.

Terms

a(0) =0a(1) =0a(2) =1a(3) =3a(4) =6a(5) =10a(6) =30a(7) =126a(8) =448a(9) =1296a(10) =4140a(11) =17380a(12) =76296a(13) =296088a(14) =1126216a(15) =4940040a(16) =23904000a(17) =110455936a(18) =489602448a(19) =2313783216a(20) =11960299360a(21) =61878663840a(22) =309644323296