Number of stacks of length 1 in all 2ndary structures of size n.

Terms

a(0) =0a(1) =0a(2) =0a(3) =1a(4) =3a(5) =6a(6) =16a(7) =43a(8) =110a(9) =284a(10) =733a(11) =1886a(12) =4853a(13) =12486a(14) =32121a(15) =82647a(16) =212699a(17) =547552a(18) =1410023a(19) =3632260a(20) =9360140a(21) =24129284a(22) =62224692a(23) =160522287a(24) =414246823a(25) =1069376386a(26) =2761502201a(27) =7133442743a(28) =18432633823a(29) =47643696626