T(n,n), array T given by A047020.

Terms

a(0) =1a(1) =1a(2) =2a(3) =5a(4) =19a(5) =66a(6) =227a(7) =851a(8) =3164a(9) =11706a(10) =44397a(11) =168814a(12) =641641a(13) =2460264a(14) =9462675a(15) =36434340a(16) =140822588a(17) =545555490a(18) =2116273293a(19) =8226372157a(20) =32029990809a(21) =124856742546a(22) =487360876726