a(n) = floor( Gamma(n+3/7)/Gamma(3/7) ).

Terms

a(0) =1a(1) =0a(2) =0a(3) =1a(4) =5a(5) =22a(6) =122a(7) =787a(8) =5852a(9) =49330a(10) =465112a(11) =4850460a(12) =55433829a(13) =688963306a(14) =9251792972a(15) =133490155743