Numbers k for which k = sigma(sigma(x)) = sigma(sigma(y)) for some x and y such that k = x + y.

Terms

a(0) =4a(1) =8a(2) =32a(3) =60a(4) =128a(5) =8192a(6) =43200a(7) =69360a(8) =120960a(9) =131072a(10) =524288a(11) =4146912a(12) =6549984a(13) =12927600a(14) =13335840a(15) =16329600a(16) =34715520a(17) =51603840a(18) =57879360a(19) =59633280a(20) =107775360a(21) =160797000a(22) =169155840a(23) =252067200a(24) =371226240a(25) =391789440a(26) =436230144a(27) =439883136a(28) =489888000a(29) =657296640