Numbers j such that sigma(sigma(j)) = k*j for some k.

Terms

a(0) =1a(1) =2a(2) =4a(3) =8a(4) =15a(5) =16a(6) =21a(7) =24a(8) =42a(9) =60a(10) =64a(11) =84a(12) =160a(13) =168a(14) =240a(15) =336a(16) =480a(17) =504a(18) =512a(19) =960a(20) =1023a(21) =1344a(22) =1536a(23) =4092a(24) =4096a(25) =10752a(26) =13824a(27) =16368a(28) =29127a(29) =32256