Multiples of 15.

Terms

a(0) =0a(1) =15a(2) =30a(3) =45a(4) =60a(5) =75a(6) =90a(7) =105a(8) =120a(9) =135a(10) =150a(11) =165a(12) =180a(13) =195a(14) =210a(15) =225a(16) =240a(17) =255a(18) =270a(19) =285a(20) =300a(21) =315a(22) =330a(23) =345a(24) =360a(25) =375a(26) =390a(27) =405a(28) =420a(29) =435