a(n) = C(1,1) + C(3,2) + C(5,3) + ... + C(2*n-1,n).

Terms

a(0) =1a(1) =4a(2) =14a(3) =49a(4) =175a(5) =637a(6) =2353a(7) =8788a(8) =33098a(9) =125476a(10) =478192a(11) =1830270a(12) =7030570a(13) =27088870a(14) =104647630a(15) =405187825a(16) =1571990935a(17) =6109558585a(18) =23782190485a(19) =92705454895a(20) =361834392115