(Translated by https://www.hiragana.jp/)
# Greetings from The On-Line Encyclopedia of Integer Sequences! http://oeis.org/ Search: id:a128858 Showing 1-1 of 1 %I A128858 #22 Apr 09 2024 14:18:51 %S A128858 1,18,28,6,42,58,22,13,44,2,108,48,21,46,148,13,78,178,6,99,18,8,228, %T A128858 7,41,6,268,15,272,66,34,28,138,112,116,179,5,378,388,18,204,418,6, %U A128858 219,32,48,66,239,81,498,508,43,506,42,60,42,284,192,90,299,84,618,48,35 %N A128858 Number of digits in A128857(n). %H A128858 A. V. Chupin, Table of n, a(n) for n = 1..1000 %F A128858 a(n) = order of 10 (mod 10*n - 1). - _Arkadiusz Wesolowski_, Nov 17 2012 %t A128858 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]]] %o A128858 (Python) %o A128858 from sympy import n_order %o A128858 def A128858(n): return n_order(10,10*n-1) # _Chai Wah Wu_, Apr 09 2024 %Y A128858 Cf. A128857. %K A128858 nonn,base %O A128858 1,2 %A A128858 Anton V. Chupin (chupin(X)icmm.ru), Apr 12 2007 %E A128858 a(10) = 2 corrected by _Gerard P. Michon_, Oct 31 2012 # Content is available under The OEIS End-User License Agreement: http://oeis.org/LICENSE