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A121090 Period of unit fractions having periodic decimal expansions. 4
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, 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, 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 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

COMMENTS

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

LINKS

Table of n, a(n) for n=0..86.

EXAMPLE

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

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

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

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

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

PROG

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

CROSSREFS

Cf. A085837, A007732.

Sequence in context: A002950 A324046 A244059 * A321991 A010135 A176401

Adjacent sequences:  A121087 A121088 A121089 * A121091 A121092 A121093

KEYWORD

nonn,base

AUTHOR

Gil Broussard, Aug 11 2006

STATUS

approved

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Last modified December 8 04:46 EST 2019. Contains 329853 sequences. (Running on oeis4.)