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A158877
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Definition of a(n): in base-n arithmetic a(n) is the smallest positive integer that is doubled when its least significant digit is moved to become the most significant digit.
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2
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OFFSET
| 3,1
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COMMENTS
| The problem has no solution in base 2, so sequence begins with the base-3 solution. The idea was suggested by a NY Times article (Sunday Magazine of Mar 29, 2009) -- in which Freeman Dyson is said to have solved the base-10 question almost instantaneously when it was posed to him -- and by the ensuing math-fun discussion.
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EXAMPLE
| Example: For n = 5, the smallest positive integer whose base-5 representation doubles when the rightmost digit is moved to become the leftmost digit is 8 [base 10] = 13 [base 5]. For 31 [base 5] = 16 [base 10].
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CROSSREFS
| See A087502 (which is the main entry for this sequence) for these numbers written in base 10. Cf. A023094, A159774.
Sequence in context: A178396 A178349 A094946 * A159774 A072140 A080467
Adjacent sequences: A158874 A158875 A158876 * A158878 A158879 A158880
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KEYWORD
| nonn,base
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AUTHOR
| Daniel Asimov (asimov(AT)msri.org), Mar 28 2009
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EXTENSIONS
| a(5) corrected by William A. Hoffman III (whoff(AT)robill.com), Apr 19 2009
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