a(n) = ceiling(n*phi^6), where phi is the golden ratio.

Terms

a(0) =0a(1) =18a(2) =36a(3) =54a(4) =72a(5) =90a(6) =108a(7) =126a(8) =144a(9) =162a(10) =180a(11) =198a(12) =216a(13) =234a(14) =252a(15) =270a(16) =288a(17) =306a(18) =323a(19) =341a(20) =359a(21) =377a(22) =395a(23) =413a(24) =431a(25) =449a(26) =467a(27) =485a(28) =503a(29) =521