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A128858
Number of digits in A128857(n).
4
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
OFFSET
1,2
LINKS
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]]]
PROG
(Python)
from sympy import n_order
def A128858(n): return n_order(10, 10*n-1) # Chai Wah Wu, Apr 09 2024
CROSSREFS
Cf. A128857.
Sequence in context: A166630 A154920 A094224 * A141782 A093648 A171221
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