Sequence with Hankel transform equal to 3^floor(n^2/3).

Terms

a(0) =1a(1) =1a(2) =2a(3) =7a(4) =32a(5) =160a(6) =830a(7) =4405a(8) =23798a(9) =130498a(10) =724748a(11) =4069258a(12) =23064608a(13) =131809108a(14) =758696492a(15) =4394825647a(16) =25600773272a(17) =149877922228a(18) =881394158558