T(n,n+1), array T given by A047020.

Terms

a(0) =1a(1) =2a(2) =5a(3) =14a(4) =47a(5) =161a(6) =558a(7) =2020a(8) =7398a(9) =27239a(10) =101807a(11) =383210a(12) =1447965a(13) =5507227a(14) =21038148a(15) =80597585a(16) =309861811a(17) =1194651520a(18) =4615681266a(19) =17872627858a(20) =69339129304a(21) =269437315070