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A128858
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Number of digits in A128857(n).
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4
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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
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OFFSET
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1,2
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LINKS
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FORMULA
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a(n) = order of 10 (mod 10*n - 1). - _Arkadiusz Wesolowski_, Nov 17 2012
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MATHEMATICA
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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]]]
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PROG
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(Python)
from sympy import n_order
def A128858(n): return n_order(10, 10*n-1) # _Chai Wah Wu_, Apr 09 2024
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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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Anton V. Chupin (chupin(X)icmm.ru), Apr 12 2007
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EXTENSIONS
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a(10) = 2 corrected by _Gerard P. Michon_, Oct 31 2012
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STATUS
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approved
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