Odd prime values of sigma(k) - phi(k) taking k in increasing order.

Terms

a(0) =5a(1) =11a(2) =7a(3) =23a(4) =11a(5) =47a(6) =79a(7) =73a(8) =67a(9) =23a(10) =191a(11) =283a(12) =383a(13) =739a(14) =47a(15) =1459a(16) =281a(17) =607a(18) =59a(19) =1153a(20) =1069a(21) =3319a(22) =83a(23) =1801a(24) =2671a(25) =3517a(26) =743a(27) =107a(28) =6679a(29) =3529