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A288157
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Number of bases b < n where the digits of n are not all different.
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1
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0, 0, 1, 2, 2, 2, 2, 3, 3, 4, 2, 4, 3, 4, 3, 5, 4, 5, 2, 5, 4, 5, 4, 6, 5, 6, 4, 5, 4, 6, 5, 7, 5, 6, 4, 8, 6, 5, 4, 7, 5, 7, 6, 6, 6, 7, 5, 8, 6, 8, 5, 6, 4, 6, 6, 7, 7, 6, 5, 11, 7, 7, 7, 10, 7, 7, 6, 7, 5, 7, 6, 11, 6, 8, 7, 7, 6, 9, 6, 9, 9, 7, 5, 10, 7, 6, 7, 9, 7, 10, 8, 10, 8, 7, 6, 10, 7, 10, 6
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OFFSET
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1,4
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LINKS
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EXAMPLE
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a(10)=4 because 10 equals 1010 base 2 (repeating both 0 and 1), 101 base 3 (repeating 1), 22 base 4 (repeating 2) and 11 base 9 (repeating 1), and 20, 14, 13, 12 in the other bases < 10, not repeating digits.
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MATHEMATICA
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Table[n - 1 - Boole[n > 1] - Count[Range[2, n - 1], b_ /; UnsameQ @@ IntegerDigits[n, b]], {n, 99}] (* Michael De Vlieger, Jun 15 2017 *)
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PROG
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(PARI) a(n) = sum(b=2, n, d = digits(n, b); #d != #Set(d)); \\ Michel Marcus, Jun 13 2017
(PARI) a(n)=my(s=sqrtint(n)); sum(b=2, s, my(d=digits(n, b)); #Set(d)!=#d) + sum(k=1, n\(s+1), n%k==0 && n/k>s+1) \\ Charles R Greathouse IV, Jun 15 2017
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CROSSREFS
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KEYWORD
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base,nonn,easy
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AUTHOR
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STATUS
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approved
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