a(n) = floor(n/7)*ceiling(n/7).

Terms

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