T(n,n+1), array T as in A047120.

Terms

a(0) =1a(1) =2a(2) =6a(3) =20a(4) =71a(5) =256a(6) =938a(7) =3480a(8) =13041a(9) =49234a(10) =186968a(11) =713428a(12) =2733218a(13) =10506788a(14) =40506442a(15) =156554820a(16) =606400307a(17) =2353368138a(18) =9148789134a(19) =35620615548a(20) =138878821241a(21) =542138013480