a(n) = T(0,n) + T(1,n-1) + ... + T(n,0), array T given by A048471.

Terms

a(0) =1a(1) =3a(2) =9a(3) =29a(4) =95a(5) =307a(6) =973a(7) =3033a(8) =9339a(9) =28511a(10) =86537a(11) =261637a(12) =788983a(13) =2375115a(14) =7141701a(15) =21457841a(16) =64439027a(17) =193448119a(18) =580606465a(19) =1742343645a(20) =5228079471a(21) =15686335523a(22) =47063200829a(23) =141197991049a(24) =423610750315