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A050725
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Decimal expansion of 4^n contains no pair of consecutive equal digits (probably finite).
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1
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0, 1, 2, 3, 4, 5, 6, 7, 10, 11, 14, 15, 16, 17, 18, 24, 27, 28, 33, 34, 40, 52, 63
(list;
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history;
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internal format)
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OFFSET
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1,3
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COMMENTS
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No additional terms up to 1200. - Harvey P. Dale, Mar 30 2011
No additional terms up to 100000. - Michel Marcus, Oct 16 2019
Half of even terms of A050723. - Joerg Arndt, Oct 16 2019
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LINKS
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Table of n, a(n) for n=1..23.
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EXAMPLE
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4^63 = 85070591730234615865843651857942052864.
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MATHEMATICA
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Select[Range[0, 70], FreeQ[Differences[IntegerDigits[4^#]], 0]&] (* Harvey P. Dale, Jul 25 2013 *)
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PROG
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(PARI) isok(n) = {my(d = digits(4^n), c = d[1]); for (i=2, #d, if (d[i] == c, return (0)); c = d[i]; ); return (1); } \\ Michel Marcus, Oct 16 2019
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CROSSREFS
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Cf. A000302, A030701, A046262, A046270.
Sequence in context: A191927 A116000 A251595 * A080571 A165805 A319975
Adjacent sequences: A050722 A050723 A050724 * A050726 A050727 A050728
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KEYWORD
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nonn,base,more
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AUTHOR
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Patrick De Geest, Sep 15 1999
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STATUS
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approved
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