a(n) = Sum_{k=0..n} floor(k*phi^2) where phi=(1+sqrt(5))/2.

Terms

a(0) =0a(1) =2a(2) =7a(3) =14a(4) =24a(5) =37a(6) =52a(7) =70a(8) =90a(9) =113a(10) =139a(11) =167a(12) =198a(13) =232a(14) =268a(15) =307a(16) =348a(17) =392a(18) =439a(19) =488a(20) =540a(21) =594a(22) =651a(23) =711a(24) =773a(25) =838a(26) =906a(27) =976a(28) =1049a(29) =1124