Sort then Add, a(1)=15.

Terms

a(0) =15a(1) =30a(2) =33a(3) =66a(4) =132a(5) =255a(6) =510a(7) =525a(8) =780a(9) =858a(10) =1446a(11) =2892a(12) =5181a(13) =6339a(14) =9708a(15) =10497a(16) =11976a(17) =23655a(18) =47211a(19) =58458a(20) =104046a(21) =105492a(22) =117951a(23) =229530a(24) =251889a(25) =377778a(26) =755556a(27) =1311123a(28) =2422356a(29) =4645812