A375998 The smallest positive number that when written in all bases 2 to n contains four or more adjacent equal digits.
15, 80, 4010, 12031, 255312, 2686719, 117178358, 436210878, 91532745555
Offset: 2
Examples
a(7) = 2686719 as 2686719 = 1010001111111011111111_2 = 12001111111010_3 = 22033323333_4 = 1141433334_5 = 133330303_6 = 31560000_7, each of which contains four or more adjacent equal digits.