Number of 3D walks of type abc.

Terms

a(0) =1a(1) =1a(2) =5a(3) =12a(4) =62a(5) =200a(6) =1065a(7) =3990a(8) =21714a(9) =89082a(10) =492366a(11) =2147376a(12) =12004740a(13) =54718092a(14) =308559537a(15) =1454116950a(16) =8255788970a(17) =39935276810a(18) =227976044010