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A113654
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Numbers k such that the square of k contains sigma(k) as a substring, in base 10.
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0
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1, 11, 101, 125, 153, 1205, 1502, 1810, 3080, 7631, 18010, 18650, 21020, 36559, 36911, 44805, 53999, 60541, 68443, 120005, 189585, 210020, 487195, 1059449, 1750004, 1800010, 1860050, 1872250, 2072139, 2170100, 2268661, 2496750
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OFFSET
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1,2
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COMMENTS
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If p = 180...01 is prime, then k = 2*5*p = 180...010, k^2 = 3240...0360...0100 and sigma(k) = 3240...036, thus k belongs to the sequence.
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LINKS
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EXAMPLE
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153^2 = 23409 and sigma(153) = 234.
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MATHEMATICA
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lst = {}; Do[If[{}!= StringPosition[ToString[n^2], ToString@DivisorSigma[1, n]], AppendTo[lst, n]], {n, 10^6}]; lst
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CROSSREFS
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KEYWORD
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base,nonn
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AUTHOR
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STATUS
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approved
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