T(2n+1,n), where T is the array in A055830.

Terms

a(0) =1a(1) =3a(2) =12a(3) =54a(4) =255a(5) =1239a(6) =6132a(7) =30744a(8) =155628a(9) =793650a(10) =4071210a(11) =20984340a(12) =108590118a(13) =563816526a(14) =2935798680a(15) =15324533448a(16) =80164934919a(17) =420151515255