a(n) = floor(binomial(n,5)/5).

Terms

a(0) =0a(1) =0a(2) =0a(3) =0a(4) =0a(5) =0a(6) =1a(7) =4a(8) =11a(9) =25a(10) =50a(11) =92a(12) =158a(13) =257a(14) =400a(15) =600a(16) =873a(17) =1237a(18) =1713a(19) =2325a(20) =3100a(21) =4069a(22) =5266a(23) =6729a(24) =8500a(25) =10626a(26) =13156a(27) =16146a(28) =19656a(29) =23751