a(n) = ceiling(binomial(n,4)/n).

Terms

a(0) =0a(1) =0a(2) =0a(3) =1a(4) =1a(5) =3a(6) =5a(7) =9a(8) =14a(9) =21a(10) =30a(11) =42a(12) =55a(13) =72a(14) =91a(15) =114a(16) =140a(17) =170a(18) =204a(19) =243a(20) =285a(21) =333a(22) =385a(23) =443a(24) =506a(25) =575a(26) =650a(27) =732a(28) =819a(29) =914