Triangle t(n,m) read by rows: t(n,m) = binomial(n,m)*3^m if m <= n/2, else t(n,m) = t(n,n-m).

Terms

a(0) =1a(1) =1a(2) =1a(3) =1a(4) =6a(5) =1a(6) =1a(7) =9a(8) =9a(9) =1a(10) =1a(11) =12a(12) =54a(13) =12a(14) =1a(15) =1a(16) =15a(17) =90a(18) =90a(19) =15a(20) =1a(21) =1a(22) =18a(23) =135a(24) =540a(25) =135a(26) =18a(27) =1a(28) =1a(29) =21