Triangle read by rows: T(n,k) = 3*T(n-1,k-1) + 3*T(n-1,k) - 2*T(n-2,k-1) with T(n,0) = T(n,n) = 1.

Terms

a(0) =1a(1) =1a(2) =1a(3) =1a(4) =4a(5) =1a(6) =1a(7) =13a(8) =13a(9) =1a(10) =1a(11) =40a(12) =70a(13) =40a(14) =1a(15) =1a(16) =121a(17) =304a(18) =304a(19) =121a(20) =1a(21) =1a(22) =364a(23) =1195a(24) =1684a(25) =1195a(26) =364a(27) =1a(28) =1a(29) =1093