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A155005
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Smallest number having exactly n divisors that are contained in its decimal representation.
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1
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1, 10, 12, 110, 120, 1020, 1200, 1248, 10250, 11250, 12480, 31248, 132600, 124800, 112500, 312480, 1248000, 1312500, 1125000, 3124800, 14437500, 16250000, 11250000, 31248000, 103125000, 144375000, 112500000, 131250000
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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COMMENTS
| A121041(a(n)) = n and A121041(m) < n for m < a(n).
Conjecture: a(5+5n)=1125*10^n for n>0. [From Robert G. Wilson, v (rgwv(AT)rgwv.com), Jan 23 2009]
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EXAMPLE
| a(4) = 110, A121041(110) = #{1, 10, 11, 110} = 4;
a(5) = 120, A121041(120) = #{1, 2, 12, 20, 120} = 5;
a(6) = 1020, A121041(1020) = #{1, 2, 10, 20, 102, 1020} = 6.
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MATHEMATICA
| f[n_] := Block[{d = Divisors@ n, len = DivisorSigma[0, n], i = 1, c = 1, s = ToString@ n}, While[i < len, If[ StringMatchQ[s, "*" <> ToString[d[[i]]] <> "*"], c++ ] ; i++ ]; c]; t = Table[0, {30}]; Do[ a = f[n]; If[ t[[a]] == 0, t[[a]] = n; Print[{a, n}]], {n, 2*10^8}] [From Robert G. Wilson, v (rgwv(AT)rgwv.com), Jan 23 2009]
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CROSSREFS
| Sequence in context: A116118 A038314 A119225 * A078217 A178639 A087392
Adjacent sequences: A155002 A155003 A155004 * A155006 A155007 A155008
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KEYWORD
| base,nonn
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AUTHOR
| Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Jan 18 2009
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EXTENSIONS
| I added a(17)-a(28). Robert G. Wilson, v (rgwv(AT)rgwv.com), Jan 23 2009
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