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A121319
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a(n) is the smallest number k such that k and 2^k have the same last n digits. Here k must have at least n digits (cf. A113627).
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4
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14, 36, 736, 8736, 48736, 948736, 2948736, 32948736, 432948736, 3432948736, 53432948736, 353432948736, 5353432948736, 75353432948736, 1075353432948736, 5075353432948736, 15075353432948736, 615075353432948736, 8615075353432948736, 98615075353432948736
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OFFSET
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1,1
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LINKS
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FORMULA
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EXAMPLE
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2^14 = 16384 and 14 end with the same single digit 4, thus a(1) = 14.
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MATHEMATICA
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f[n_] := Block[{k = If[n == 1, 2, 10], m = 10^n}, While[ PowerMod[2, k, m] != Mod[k, m], k += 2]; k]; Do[ Print@f@n, {n, 9}] (* Robert G. Wilson v *)
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PROG
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(PARI) A121319(n) = { local(k, tn); tn=10^n ; forstep(k=2, 1000000000, 2, if ( k % tn == (2^k) % tn, return(k) ; ) ; ) ; return(0) ; } { for(n = 1, 13, print( A121319(n)) ; ) ; } \\ R. J. Mathar, Aug 27 2006
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CROSSREFS
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KEYWORD
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nonn,base
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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