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A275782
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a(n) = smallest k such that the digits of exactly n nonnegative numbers are a subsequence of the digits of k.
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1
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0, 11, 10, 100, 101, 102, 120, 1002, 1022, 1012, 1021, 1023, 1201, 1203, 1230, 10023, 10121, 10120, 10201, 10123, 10232, 10213, 10231, 10234, 12132, 12013, 12031, 12034, 12301, 12304, 12340, 100234, 101201, 101213, 101232, 101203, 101231, 101230, 102031, 101234, 102132, 102130, 102301, 102134, 102342
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OFFSET
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1,2
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LINKS
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EXAMPLE
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The digits of exactly 19 numbers are a subsequence of 10201: 0, 1, 2, 10, 11, 12, 20, 21, 100, 101, 102, 120, 121, 201, 1001, 1020, 1021, 1201, and 10201. No number smaller than 10201 has this property. Hence a(19) = 10201.
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MATHEMATICA
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t = Table[Length@ Union@ Map[FromDigits, Subsets@ IntegerDigits@ n /. {} -> Nothing], {n, 0, 103000}]; Table[FirstPosition[t, n] - 1, {n, Max@ t}] // Flatten (* Michael De Vlieger, Aug 08 2016, Version 10.2 *)
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CROSSREFS
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KEYWORD
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nonn,base
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AUTHOR
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STATUS
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approved
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