Basis for code in A075943.

Terms

a(0) =511a(1) =15887a(2) =116275a(3) =412245a(4) =693418a(5) =3165290a(6) =12603032a(7) =21139155a(8) =38803550a(9) =201349286a(10) =336626733a(11) =609260174a(12) =3221261509a(13) =5374090380a(14) =25769843817a(15) =43016936625a(16) =78384372260a(17) =412317013686a(18) =687266122367