a(n) = T(2*n, n+3), T given by A027935.

Terms

a(0) =1a(1) =29a(2) =247a(3) =1300a(4) =5270a(5) =18228a(6) =56967a(7) =166681a(8) =467301a(9) =1274856a(10) =3419252a(11) =9076280a(12) =23945893a(13) =62955061a(14) =165188091a(15) =432974764a(16) =1134224458a(17) =2970340412a(18) =7777628427a(19) =20363608737a(20) =53314542953a(21) =139581703056a(22) =365432651464a(23) =956718812272