Number of reduced words of length n in the Weyl group A_18.

Terms

a(0) =1a(1) =18a(2) =170a(3) =1121a(4) =5795a(5) =25005a(6) =93651a(7) =312646a(8) =948328a(9) =2651355a(10) =6908989a(11) =16929266a(12) =39287173a(13) =86859412a(14) =183856635a(15) =374153699a(16) =734644291a(17) =1396030396a(18) =2574320659a(19) =4617369760a(20) =8072048882a(21) =13779087108a(22) =23004239550a(23) =37616173304a(24) =60323245445a(25) =94983079721a(26) =147000403785