a(n) = T(2*n+1, n+3), T given by A026998.

Terms

a(0) =1a(1) =34a(2) =281a(3) =1397a(4) =5353a(5) =17643a(6) =53062a(7) =150833a(8) =414210a(9) =1114160a(10) =2960806a(11) =7814074a(12) =20544191a(13) =53902532a(14) =141273663a(15) =370060623a(16) =969088727a(17) =2537431693a(18) =6643486220a(19) =17393369595a(20) =45537037936a(21) =119218243314a(22) =312118286876a(23) =817137321092