Duplicate of A020883.

Terms

a(0) =4a(1) =12a(2) =15a(3) =21a(4) =24a(5) =35a(6) =40a(7) =45a(8) =55a(9) =56a(10) =60a(11) =63a(12) =72a(13) =77a(14) =80a(15) =84a(16) =91a(17) =99a(18) =105a(19) =112a(20) =117