a(n) = (5*n + 4)*binomial(n+7,7)/4.

Terms

a(0) =1a(1) =18a(2) =126a(3) =570a(4) =1980a(5) =5742a(6) =14586a(7) =33462a(8) =70785a(9) =140140a(10) =262548a(11) =469404a(12) =806208a(13) =1337220a(14) =2151180a(15) =3368244a(16) =5148297a(17) =7700814a(18) =11296450a(19) =16280550a(20) =23088780a(21) =32265090a(22) =44482230a(23) =60565050a(24) =81516825a(25) =108548856a(26) =143113608a(27) =186941656a(28) =242082720a(29) =310951080