Triangle T(n,k) = 2^(k-1)*n*binomial(n-k,2*k-2)/(n-3*k+3) if k<n/3+1, else T(n,k)=1.

Terms

a(0) =1a(1) =1a(2) =1a(3) =8a(4) =1a(5) =15a(6) =1a(7) =24a(8) =1a(9) =1a(10) =35a(11) =28a(12) =1a(13) =48a(14) =80a(15) =1a(16) =1a(17) =63a(18) =180a(19) =1a(20) =1a(21) =80a(22) =350a(23) =80a(24) =1a(25) =1a(26) =99a(27) =616a(28) =308a(29) =1