a(n) = floor( Gamma(n+6/7)/Gamma(6/7) ).

Terms

a(0) =1a(1) =0a(2) =1a(3) =4a(4) =17a(5) =85a(6) =499a(7) =3422a(8) =26888a(9) =238157a(10) =2347553a(11) =25487720a(12) =302211542a(13) =3885576978a(14) =53842995267a(15) =799953072548