Duplicate of A137551.

Terms

a(0) =1a(1) =2a(2) =5a(3) =14a(4) =43a(5) =144a(6) =525a(7) =2084a(8) =9005a(9) =42288a(10) =215111a(11) =1179738a(12) =6937765a(13) =43504598a(14) =289356385a(15) =2031636826a(16) =14995775647a(17) =115943399636a(18) =936138957225