T(n,n-2), array T as in A047030.

Terms

a(0) =1a(1) =1a(2) =4a(3) =18a(4) =74a(5) =295a(6) =1157a(7) =4519a(8) =17620a(9) =68667a(10) =267614a(11) =1043446a(12) =4071222a(13) =15897050a(14) =62124041a(15) =242971209a(16) =951030540a(17) =3725346595a(18) =14603504405a(19) =57286230209a(20) =224869490582a(21) =883247932875