Number of binary sequences of length 2n and curling number 1.

Terms

a(0) =2a(1) =6a(2) =20a(3) =74a(4) =286a(5) =1124a(6) =4460a(7) =17768a(8) =70930a(9) =283440a(10) =1133200a(11) =4531686a(12) =18124522a(13) =72493652a(14) =289965744a(15) =1159845258a(16) =4639345612a(17) =18557311624a(18) =74229104872a(19) =296916136278