Numbers k such that sigma((k-1)/2) + tau((k-1)/2) is prime.

Terms

a(0) =3a(1) =5a(2) =17a(3) =257a(4) =325a(5) =1025a(6) =65537a(7) =82945a(8) =202501a(9) =250001a(10) =2829125a(11) =7496645a(12) =10240001a(13) =13675205a(14) =16000001a(15) =27060805a(16) =48469445a(17) =71402501a(18) =133448705a(19) =150062501a(20) =156250001a(21) =172186885a(22) =182250001a(23) =343064485a(24) =354117125a(25) =453519617a(26) =467943425a(27) =1235663105