When the numerator - denominator (A064169) in n-th harmonic number is prime.

Terms

a(0) =3a(1) =4a(2) =6a(3) =7a(4) =10a(5) =19a(6) =20a(7) =26a(8) =30a(9) =31a(10) =33a(11) =40a(12) =63a(13) =85a(14) =92a(15) =100a(16) =126a(17) =131a(18) =185a(19) =196a(20) =200a(21) =204a(22) =242a(23) =246a(24) =272a(25) =274a(26) =282a(27) =379a(28) =553a(29) =572