Average of proper divisors excluding 1 is an integer.

Terms

a(0) =4a(1) =8a(2) =9a(3) =15a(4) =18a(5) =21a(6) =25a(7) =27a(8) =33a(9) =35a(10) =39a(11) =45a(12) =49a(13) =51a(14) =55a(15) =57a(16) =63a(17) =65a(18) =69a(19) =75a(20) =77a(21) =81a(22) =85a(23) =87a(24) =91a(25) =93a(26) =95a(27) =98a(28) =99a(29) =111