Dirichlet convolution of 3^(n-1) with Catalan numbers.

Terms

a(0) =1a(1) =4a(2) =11a(3) =35a(4) =95a(5) =300a(6) =861a(7) =2658a(8) =8009a(9) =24668a(10) =75845a(11) =236401a(12) =739453a(13) =2338348a(14) =7457697a(15) =24047361a(16) =78404391a(17) =258796668a(18) =865059189a(19) =2929559709a(20) =10050907467a(21) =34926729660a(22) =122863623249a(23) =437203156566