Number of permutations of n elements whose unsigned reversal distance is k.

Terms

a(0) =1a(1) =1a(2) =1a(3) =1a(4) =3a(5) =2a(6) =1a(7) =6a(8) =15a(9) =2a(10) =1a(11) =10a(12) =51a(13) =56a(14) =2a(15) =1a(16) =15a(17) =127a(18) =390a(19) =185a(20) =2a(21) =1a(22) =21a(23) =263a(24) =1562a(25) =2543a(26) =648a(27) =2a(28) =1a(29) =28