a(n) = floor(n/4)*floor((n+1)/4).

Terms

a(0) =0a(1) =0a(2) =0a(3) =0a(4) =1a(5) =1a(6) =1a(7) =2a(8) =4a(9) =4a(10) =4a(11) =6a(12) =9a(13) =9a(14) =9a(15) =12a(16) =16a(17) =16a(18) =16a(19) =20a(20) =25a(21) =25a(22) =25a(23) =30a(24) =36a(25) =36a(26) =36a(27) =42a(28) =49a(29) =49