a(n) = T(2*n, n+2), T given by A027011.

Terms

a(0) =1a(1) =8a(2) =107a(3) =654a(4) =2801a(5) =9859a(6) =30869a(7) =89951a(8) =250780a(9) =680665a(10) =1818310a(11) =4813018a(12) =12674542a(13) =33283434a(14) =87272241a(15) =228658744a(16) =598864479a(17) =1568137061a(18) =4105798635a(19) =10749568905a(20) =28143285770a(21) =73680744203a(22) =192899492252a(23) =505018380164