a(n) = floor( Gamma(n+2/7)/Gamma(2/7) ).

Terms

a(0) =1a(1) =0a(2) =0a(3) =0a(4) =2a(5) =11a(6) =62a(7) =392a(8) =2862a(9) =23714a(10) =220204a(11) =2264965a(12) =25561751a(13) =314044378a(14) =4172303889a(15) =59604341272a(16) =911094930876