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 A121090 Period of unit fractions having periodic decimal expansions. 4

%I

%S 1,1,6,1,2,1,6,6,1,16,1,18,6,2,22,1,6,3,6,28,1,15,2,16,6,1,3,18,6,5,6,

%T 21,2,1,22,46,1,42,16,6,13,3,2,6,18,28,58,1,60,15,6,6,2,33,16,22,6,35,

%U 1,8,3,1,18,6,6,13,9,5,41,6,16,21,28,2,44,1,6,22,15,46,18,1,96,42,2,4,16

%N Period of unit fractions having periodic decimal expansions.

%C See A007732, which is the main entry for this sequence.

%e The first unit fraction considered is 1/3 because both 1/1 and 1/2 have finite decimal expansions.

%e a(1) = 1 because 1/3=.33333... whose repeating portion, 3, is of length 1.

%e Note: 1/4 and 1/5 are skipped because their decimal expansions are finite.

%e a(2) = 1 because 1/6=.166666... whose repeating portion, 6, is of length 1.

%e a(3) = 6 because 1/7 =.142857142857... whose repeating portion, 142857, is of length 6.

%o //pseudocode next=1 for n = 1 to infinity if periodic(decimalExpansion(1/n)) = TRUE a(next++) = strLen(repeatingGroup(decimalExpansion(1/n))) next n

%Y Cf. A085837, A007732.

%K nonn,base

%O 0,3

%A _Gil Broussard_, Aug 11 2006

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Last modified January 26 01:48 EST 2020. Contains 331270 sequences. (Running on oeis4.)