a(n) = T(2*n+1, n), array T as in A047080.

Terms

a(0) =1a(1) =2a(2) =5a(3) =15a(4) =46a(5) =143a(6) =450a(7) =1429a(8) =4570a(9) =14698a(10) =47491a(11) =154042a(12) =501283a(13) =1635835a(14) =5351138a(15) =17541671a(16) =57610988a(17) =189521640a(18) =624389105a(19) =2059824523a(20) =6803433916a(21) =22495796651a(22) =74457478476a(23) =246667937610a(24) =817866796549