Partial sums of A069996.

Terms

a(0) =1a(1) =13a(2) =94a(3) =526a(4) =2551a(5) =11299a(6) =47020a(7) =186988a(8) =718429a(9) =2686729a(10) =9831658a(11) =35340826a(12) =125154355a(13) =437641663a(14) =1513809688a(15) =5187129880a(16) =17627632249a(17) =59469045061a(18) =199327841590a(19) =664232428390