a(n) = ceiling(n^2/5).

Terms

a(0) =0a(1) =1a(2) =1a(3) =2a(4) =4a(5) =5a(6) =8a(7) =10a(8) =13a(9) =17a(10) =20a(11) =25a(12) =29a(13) =34a(14) =40a(15) =45a(16) =52a(17) =58a(18) =65a(19) =73a(20) =80a(21) =89a(22) =97a(23) =106a(24) =116a(25) =125a(26) =136a(27) =146a(28) =157a(29) =169