Partial sums of Catalan numbers (A000108).

Terms

a(0) =1a(1) =2a(2) =4a(3) =9a(4) =23a(5) =65a(6) =197a(7) =626a(8) =2056a(9) =6918a(10) =23714a(11) =82500a(12) =290512a(13) =1033412a(14) =3707852a(15) =13402697a(16) =48760367a(17) =178405157a(18) =656043857a(19) =2423307047a(20) =8987427467a(21) =33453694487a(22) =124936258127a(23) =467995871777