Multiples of 18.

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) =324a(19) =342a(20) =360a(21) =378a(22) =396a(23) =414a(24) =432a(25) =450a(26) =468a(27) =486a(28) =504a(29) =522