Numbers k such that (sigma(k)+sigma(k+1))/sigma(2*k+1) is an integer, where sigma = A000203.

Terms

a(0) =1a(1) =4a(2) =215a(3) =646a(4) =923a(5) =944a(6) =1096a(7) =1715a(8) =2379a(9) =5355a(10) =16174a(11) =22891a(12) =38429a(13) =64672a(14) =87584a(15) =110483a(16) =212795a(17) =291039a(18) =353110a(19) =468970a(20) =515698a(21) =733570a(22) =1016519a(23) =1051644a(24) =1198139a(25) =1317343a(26) =1633213a(27) =1735288a(28) =2026945a(29) =2093506