A290969 The least positive integer that is a repdigit with length > 2 in exactly n bases.

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

Offset: 0

Author

Bernard Schott, Aug 16 2017

Keywords

• nonn
• base
• more

Comments

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

a(7) and following terms > 3*10^9. - Giovanni Resta, Aug 16 2017

a(7) <= 2^36-1 and a(8) <= 2^48-1. - Michel Marcus, Aug 17 2017

In fact, we have equality in both cases. - Rémy Sigrist, Aug 21 2017

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

Examples

			a(1) = 7 = 111_2.
a(2) = 31 = 11111_2 = 111_5.
a(3) = 32767 = (R_15)_2 = 77777_8 = (31,31,31)_32.
		

Crossrefs

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

Extensions

a(7) from Rémy Sigrist, Aug 19 2017

a(8) from Rémy Sigrist, Aug 21 2017