a(n) = T(2*n, n+3), T given by A026998.

Terms

a(0) =1a(1) =43a(2) =431a(3) =2482a(4) =10636a(5) =38138a(6) =122069a(7) =362853a(8) =1027843a(9) =2822668a(10) =7601784a(11) =20228876a(12) =53447609a(13) =140633575a(14) =369179479a(15) =967898846a(16) =2535852052a(17) =6641420806a(18) =17390705661a(19) =45533644161a(20) =119213967867a(21) =312112955384a(22) =817130734512