Diagonal of table A062104.

Terms

a(0) =0a(1) =1a(2) =3a(3) =10a(4) =30a(5) =90a(6) =270a(7) =810a(8) =2430a(9) =7290a(10) =21870a(11) =65610a(12) =196830a(13) =590490a(14) =1771470a(15) =5314410a(16) =15943230a(17) =47829690a(18) =143489070a(19) =430467210a(20) =1291401630a(21) =3874204890a(22) =11622614670a(23) =34867844010a(24) =104603532030a(25) =313810596090a(26) =941431788270