Integers k such that numerator and denominator of sigma(k)/k are both prime.

Terms

a(0) =2a(1) =12a(2) =24a(3) =90a(4) =234a(5) =528a(6) =588a(7) =1456a(8) =4320a(9) =4680a(10) =9024a(11) =11466a(12) =26208a(13) =35640a(14) =55104a(15) =55552a(16) =90816a(17) =114660a(18) =121024a(19) =123648a(20) =185562a(21) =199584a(22) =297600a(23) =510720a(24) =674880a(25) =2142720a(26) =2190336a(27) =4112640a(28) =4316928a(29) =5322240