a(n) = floor( n*(n-1)*(n-2)*(n-3)/29 ).

Terms

a(0) =0a(1) =0a(2) =0a(3) =0a(4) =0a(5) =4a(6) =12a(7) =28a(8) =57a(9) =104a(10) =173a(11) =273a(12) =409a(13) =591a(14) =828a(15) =1129a(16) =1506a(17) =1969a(18) =2532a(19) =3207a(20) =4009a(21) =4953a(22) =6053a(23) =7328a(24) =8793a(25) =10468a(26) =12372a(27) =14524a(28) =16944a(29) =19656