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A135549
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Number of bases b, 1 < b < n-1, in which n is a palindrome.
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9
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0, 0, 0, 0, 0, 1, 0, 1, 1, 1, 2, 0, 1, 1, 1, 2, 2, 2, 2, 0, 2, 3, 1, 1, 3, 1, 3, 2, 3, 1, 2, 2, 2, 2, 2, 1, 4, 1, 2, 1, 4, 1, 3, 1, 2, 3, 3, 0, 4, 1, 3, 3, 4, 0, 3, 3, 3, 3, 1, 1, 5, 1, 2, 4, 3, 4, 3, 2, 3, 1, 3, 1, 5, 2, 2, 2, 2, 1, 5, 0, 6, 2, 3, 1, 5, 4, 2, 1, 4, 1, 4, 3, 4, 3, 1, 1, 5, 1, 4, 3, 6, 1, 3, 0, 5
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OFFSET
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0,11
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COMMENTS
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Every integer n is a palindrome when expressed in unary, or in base n-1 (where it will be 11). So here we assume 1 < b < n-1.
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LINKS
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FORMULA
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MATHEMATICA
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a = {0, 0, 0}; For[n = 4, n < 100, n++, c = 0; For[b = 2, b < n - 1, b++, If[IntegerDigits[n, b] == Reverse[IntegerDigits[n, b]], c++ ]]; AppendTo[a, c]]; a (* Stefan Steinerberger, Feb 27 2008 *)
Table[cnt=0; Do[d=IntegerDigits[n, b]; If[d==Reverse[d], cnt++ ], {b, 2, n-2}]; cnt, {n, 0, 100}] (* T. D. Noe, Feb 28 2008 *)
Table[Total[Boole[Table[PalindromeQ[IntegerDigits[n, b]], {b, 2, n-2}]]], {n, 0, 120}] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Apr 14 2020 *)
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CROSSREFS
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Cf. A016038 (non-palindromic numbers in any base 1 < b < n-1)
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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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