Numbers k such that sigma(2*k-1) is a prime p.

Terms

a(0) =5a(1) =13a(2) =145a(3) =365a(4) =841a(5) =1201a(6) =1741a(7) =2521a(8) =3961a(9) =5101a(10) =7813a(11) =8581a(12) =13945a(13) =14281a(14) =14965a(15) =41761a(16) =42925a(17) =73345a(18) =139921a(19) =229165a(20) =245701a(21) =265721a(22) =276025a(23) =289561a(24) =298765a(25) =341965a(26) =351961a(27) =353641a(28) =367225a(29) =414961