a(n) = CatalanNumber(n+1)*n*(1+3*n)/(6+2*n).

Terms

a(0) =0a(1) =1a(2) =7a(3) =35a(4) =156a(5) =660a(6) =2717a(7) =11011a(8) =44200a(9) =176358a(10) =700910a(11) =2778446a(12) =10994920a(13) =43459650a(14) =171655785a(15) =677688675a(16) =2674776720a(17) =10555815270a(18) =41656918050a(19) =164401379610a(20) =648887951400