Number of triangle-free configurations of type (n_3).

Terms

a(0) =0a(1) =0a(2) =0a(3) =0a(4) =0a(5) =0a(6) =0a(7) =0a(8) =0a(9) =0a(10) =0a(11) =0a(12) =0a(13) =0a(14) =1a(15) =0a(16) =1a(17) =4a(18) =14a(19) =162a(20) =4713a(21) =157211