T(n,n+1), array T as in A047030.

Terms

a(0) =1a(1) =2a(2) =6a(3) =20a(4) =69a(5) =246a(6) =896a(7) =3312a(8) =12371a(9) =46582a(10) =176528a(11) =672464a(12) =2572700a(13) =9878116a(14) =38044450a(15) =146911680a(16) =568617615a(17) =2205268306a(18) =8567986878a(19) =33341710740a(20) =129932332749a(21) =506997589626