a(n) = floor(n*(n-1)/17).

Terms

a(0) =0a(1) =0a(2) =0a(3) =0a(4) =0a(5) =1a(6) =1a(7) =2a(8) =3a(9) =4a(10) =5a(11) =6a(12) =7a(13) =9a(14) =10a(15) =12a(16) =14a(17) =16a(18) =18a(19) =20a(20) =22a(21) =24a(22) =27a(23) =29a(24) =32a(25) =35a(26) =38a(27) =41a(28) =44a(29) =47