A062691 - OEIS

A062691

Triangular numbers that contain exactly 2 different digits.

10, 15, 21, 28, 36, 45, 78, 91, 171, 300, 595, 990, 1711, 2211, 3003, 5050, 5151, 5565, 5995, 6555, 8778, 10011, 66066, 222111, 255255, 333336, 500500, 600060, 828828, 887778, 1188111, 5656566, 22221111, 50005000, 51151555, 88877778, 2222211111, 5000050000

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OFFSET

1,1

COMMENTS

For n > 2, A309597(n) is a term. - Seiichi Manyama, Sep 15 2019

LINKS

Seiichi Manyama, Table of n, a(n) for n = 1..51

EXAMPLE

300 is triangular and contains the digits 0 and 3.

MATHEMATICA

Select[Accumulate[Range[14000]], Count[DigitCount[#], Except[0]]==2&] (* Harvey P. Dale, Nov 27 2011 *)

PROG