Numbers of the form (5^{mr}-1)/(5^r-1) for positive integers m, r.

Terms

a(0) =1a(1) =6a(2) =26a(3) =31a(4) =126a(5) =156a(6) =626a(7) =651a(8) =781a(9) =3126a(10) =3906a(11) =15626a(12) =15751a(13) =16276a(14) =19531a(15) =78126a(16) =97656a(17) =390626a(18) =391251a(19) =406901a(20) =488281a(21) =1953126a(22) =1968876a(23) =2441406a(24) =9765626a(25) =9768751a(26) =10172526a(27) =12207031a(28) =48828126a(29) =61035156