a(n) = floor(n*(n-1)/16).

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) =8a(13) =9a(14) =11a(15) =13a(16) =15a(17) =17a(18) =19a(19) =21a(20) =23a(21) =26a(22) =28a(23) =31a(24) =34a(25) =37a(26) =40a(27) =43a(28) =47a(29) =50