Numbers of the form (3^s+1)/(3^r+1) for s > 1, 1 <= r <= s-1.

Terms

a(0) =7a(1) =61a(2) =73a(3) =547a(4) =4921a(5) =703a(6) =5905a(7) =44287a(8) =6481a(9) =398581a(10) =478297a(11) =3587227a(12) =512461a(13) =58807a(14) =32285041a(15) =38742049a(16) =530713a(17) =290565367a(18) =42521761a(19) =2615088301a(20) =373584043a(21) =4780783a(22) =3138105961a(23) =23535794707a(24) =43040161a(25) =211822152361a(26) =3472494301