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A061280
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Smallest base b >= 2 for which b^n contains n as a substring.
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3
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10, 5, 7, 7, 5, 2, 3, 7, 3, 2, 11, 7, 6, 25, 7, 11, 4, 8, 5, 7, 6, 6, 6, 3, 4, 9, 17, 3, 6, 13, 8, 5, 8, 5, 2, 2, 2, 8, 6, 6, 5, 4, 7, 2, 6, 9, 8, 6, 2, 4, 2, 8, 6, 5, 5, 5, 3, 8, 4, 2, 3, 3, 6, 5, 6, 12, 2, 6, 3, 5, 3, 2, 2, 6, 5, 6, 3, 3, 4, 3, 4, 2, 3, 4, 2, 4, 3, 7, 2, 8, 8, 4, 2, 6, 3, 4, 7, 6, 7, 7
(list;
graph;
refs;
listen;
history;
text;
internal format)
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OFFSET
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1,1
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LINKS
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EXAMPLE
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a(3) = 7 since 7^1 contains no 1, 7^2 contains no 2 and 7^3 contains a 3.
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MAPLE
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a:= proc(n) local b; for b from 2 while
searchtext(""||n, ""||(b^n))=0 do od; b
end:
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MATHEMATICA
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Table[b = 2; While[Length@ SequencePosition[IntegerDigits[b^n], IntegerDigits[n]] == 0, b++]; b, {n, 120}] (* Michael De Vlieger, Sep 28 2016, Version 10.1 *)
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PROG
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(Python)
def a(n):
b, s = 2, str(n)
while s not in str(b**n): b += 1
return b
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CROSSREFS
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KEYWORD
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AUTHOR
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STATUS
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approved
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