Numbers n such that sigma(n-1) + sigma(n+1) = sigma(2n).

Terms

a(0) =309a(1) =425a(2) =2135a(3) =2913a(4) =6861a(5) =20155a(6) =37415a(7) =45155a(8) =74875a(9) =329841a(10) =4720281a(11) =6385749a(12) =7030911a(13) =11606649a(14) =13954745a(15) =20920075a(16) =22436225a(17) =22937785a(18) =37760631a(19) =38748291a(20) =81607505a(21) =85815925a(22) =95375589a(23) =114195965a(24) =115314295a(25) =122491401a(26) =132765639