a(n) = floor( Gamma(n+2/9) / Gamma(2/9) ).

Terms

a(0) =1a(1) =0a(2) =0a(3) =0a(4) =1a(5) =8a(6) =42a(7) =266a(8) =1927a(9) =15844a(10) =146122a(11) =1493700a(12) =16762639a(13) =204876708a(14) =2708925368a(15) =38526938568a(16) =586465620430