Number of permutations of (1,...,n) having n-2 inversions (n>=2).

Terms

a(0) =1a(1) =2a(2) =5a(3) =15a(4) =49a(5) =169a(6) =602a(7) =2191a(8) =8095a(9) =30239a(10) =113906a(11) =431886a(12) =1646177a(13) =6301715a(14) =24210652a(15) =93299841a(16) =360490592a(17) =1396030396a(18) =5417028610a(19) =21056764914a(20) =81978913225a(21) =319610939055