Number of involutions of length n having exactly n inversions.

Terms

a(0) =1a(1) =0a(2) =0a(3) =1a(4) =1a(5) =2a(6) =10a(7) =17a(8) =39a(9) =119a(10) =254a(11) =613a(12) =1623a(13) =3791a(14) =9281a(15) =23469a(16) =56823a(17) =140035a(18) =349167a(19) =857868a(20) =2122297a(21) =5274213a(22) =13044870a(23) =32357838a(24) =80421284a(25) =199613489a(26) =496144310a(27) =1234420850a(28) =3070773600a(29) =7644879181