Planar trees where no branch is identical to its adjacent neighbor.

Terms

a(0) =1a(1) =1a(2) =0a(3) =1a(4) =0a(5) =1a(6) =3a(7) =7a(8) =14a(9) =43a(10) =115a(11) =326a(12) =931a(13) =2719a(14) =7979a(15) =23804a(16) =71418a(17) =216444a(18) =660276a(19) =2028558a(20) =6268350a(21) =19479746a(22) =60835542a(23) =190881085a(24) =601459251a(25) =1902680249a(26) =6040955223a(27) =19245061851a(28) =61503863732a(29) =197135868680