Number of permutations of [1,2,...,n] with n-1 inversions.

Terms

a(0) =1a(1) =1a(2) =2a(3) =6a(4) =20a(5) =71a(6) =259a(7) =961a(8) =3606a(9) =13640a(10) =51909a(11) =198497a(12) =762007a(13) =2934764a(14) =11333950a(15) =43874857a(16) =170193528a(17) =661386105a(18) =2574320659a(19) =10034398370a(20) =39163212165a(21) =153027659730a(22) =598577118991