A290969 - OEIS

%I #77 Aug 27 2017 10:06:01

%S 1,7,31,32767,4095,435356467,16777215,68719476735,281474976710655

%N The least positive integer that is a repdigit with length > 2 in exactly n bases.

%C a(10) <= 1152921504606846975 = 2^60 - 1.

%C a(7) and following terms > 3*10^9. - _Giovanni Resta_, Aug 16 2017

%C a(7) <= 2^36-1 and a(8) <= 2^48-1. - _Michel Marcus_, Aug 17 2017

%C In fact, we have equality in both cases. - _Rémy Sigrist_, Aug 21 2017

%C Except for a(5) = (6^12 - 1) / 5, all the numbers in the data through a(8) are Mersenne numbers A000225. - _Bernard Schott_, Aug 27 2017

%e a(1) = 7 = 111_2.

%e a(2) = 31 = 11111_2 = 111_5.

%e a(3) = 32767 = (R_15)_2 = 77777_8 = (31,31,31)_32.

%Y Cf. A000225, A053696, A125134, A167782, A167783, A290869.

%K nonn,base,more

%O 0,2

%A _Bernard Schott_, Aug 16 2017

%E a(7) from _Rémy Sigrist_, Aug 19 2017

%E a(8) from _Rémy Sigrist_, Aug 21 2017