a(n) = T(0,n), array T given by A048505.

Terms

a(0) =1a(1) =2a(2) =7a(3) =25a(4) =81a(5) =241a(6) =673a(7) =1793a(8) =4609a(9) =11521a(10) =28161a(11) =67585a(12) =159745a(13) =372737a(14) =860161a(15) =1966081a(16) =4456449a(17) =10027009a(18) =22413313a(19) =49807361a(20) =110100481a(21) =242221057a(22) =530579457a(23) =1157627905a(24) =2516582401a(25) =5452595201a(26) =11777605633a(27) =25367150593a(28) =54492397569a(29) =116769423361