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 A062691 Triangular numbers that contain exactly 2 different digits. 11
 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 (list; graph; refs; listen; history; text; internal format)
 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 (PARI) for(k=0, 1e5, if(#Set(digits(j=k*(k+1)/2))==2, print1(j", "))) \\ Seiichi Manyama, Sep 15 2019 CROSSREFS Cf. A000217, A045914 (all digits the same), A213516, A213518, A309597. Sequence in context: A098564 A168103 A322045 * A257630 A129496 A075520 Adjacent sequences:  A062688 A062689 A062690 * A062692 A062693 A062694 KEYWORD base,easy,nonn AUTHOR Erich Friedman, Jul 04 2001 STATUS approved

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Last modified June 22 21:29 EDT 2021. Contains 345393 sequences. (Running on oeis4.)