n-th composite is sum of first k composites for some k.

Terms

a(0) =1a(1) =5a(2) =10a(3) =17a(4) =33a(5) =44a(6) =56a(7) =69a(8) =82a(9) =99a(10) =116a(11) =134a(12) =175a(13) =196a(14) =242a(15) =267a(16) =321a(17) =349a(18) =377a(19) =408a(20) =442a(21) =475a(22) =507a(23) =542a(24) =581a(25) =619a(26) =659a(27) =700a(28) =741a(29) =785