Numbers of the form (7^{mr}-1)/(7^r-1) for positive integers m, r.

Terms

a(0) =1a(1) =8a(2) =50a(3) =57a(4) =344a(5) =400a(6) =2402a(7) =2451a(8) =2801a(9) =16808a(10) =19608a(11) =117650a(12) =117993a(13) =120100a(14) =137257a(15) =823544a(16) =960800a(17) =5764802a(18) =5767203a(19) =5884901a(20) =6725601a(21) =40353608a(22) =40471600a(23) =47079208a(24) =282475250a(25) =282492057a(26) =288360150a(27) =329554457a(28) =1977326744a(29) =2306881200