a(n) = T(2*n+1, n), array T as in A054106.

Terms

a(0) =1a(1) =2a(2) =8a(3) =27a(4) =99a(5) =363a(6) =1353a(7) =5082a(8) =19228a(9) =73150a(10) =279566a(11) =1072512a(12) =4127788a(13) =15930512a(14) =61628248a(15) =238911947a(16) =927891163a(17) =3609676487a(18) =14062955413a(19) =54860308997a(20) =214268628223a(21) =837780853637