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A128858 Number of digits in A128857(n). 2
1, 18, 28, 6, 42, 58, 22, 13, 44, 2, 108, 48, 21, 46, 148, 13, 78, 178, 6, 99, 18, 8, 228, 7, 41, 6, 268, 15, 272, 66, 34, 28, 138, 112, 116, 179, 5, 378, 388, 18, 204, 418, 6, 219, 32, 48, 66, 239, 81, 498, 508, 43, 506, 42, 60, 42, 284, 192, 90, 299, 84, 618, 48, 35 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

A. V. Chupin, Table of n, a(n) for n = 1..1000

FORMULA

a(n) = order of 10 (mod 10*n - 1). - Arkadiusz Wesolowski, Nov 17 2012

MATHEMATICA

Give[a_, n_]:=Block[{d=Floor[Log[10, n]]+1, m=(10n-1)/GCD[10n-1, a]}, If[m?1, While[PowerMod[10, d, m]!=N, d++ ], d=1]; ((10^(d+1)-1) a n)/(10n-1)]; Length[IntegerDigits[Give[1, n]]]

CROSSREFS

Sequence in context: A166630 A154920 A094224 * A141782 A093648 A171221

Adjacent sequences:  A128855 A128856 A128857 * A128859 A128860 A128861

KEYWORD

nonn,base

AUTHOR

Anton V. Chupin (chupin(X)icmm.ru), Apr 12, 2007

EXTENSIONS

a(10) = 2 corrected by Gerard P. Michon, Oct 31 2012

STATUS

approved

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Last modified April 28 18:26 EDT 2017. Contains 285579 sequences.