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A197224 Power of 2 which is the period length of the decimal fraction 1/A072982(n). 2
0, 1, 4, 3, 2, 3, 8, 5, 5, 5, 5, 9, 8, 6, 16, 5, 8, 6, 10, 16, 4, 6, 9, 17, 20, 21, 18, 10, 13, 19, 7, 27, 9, 30, 9, 12, 20, 30, 36 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

This means that the fraction 1/52613349377 repeats every 2^30 terms! Every term with value up to 5 is accounted for. The last value of 6 occurs for 834427406578561, which is not in A072982 because there are unknown factors of 10^2^e+1 smaller than this number.

LINKS

Table of n, a(n) for n=1..39.

Hans Riesel, Some factors of the numbers Gn = 6^2^n+1 and Hn = 10^2^n+1, Math. Comp. 23 (1969), p. 413-415. With errata reported in Math. Comp. 24 (1970), p. 243.

MATHEMATICA

A072982 = {3, 11, 17, 73, 101, 137, 257, 353, 449, 641, 1409, 10753, 15361, 19841, 65537, 69857, 453377, 976193, 1514497, 5767169, 5882353, 6187457, 8253953, 8257537, 70254593, 167772161, 175636481, 302078977, 458924033, 639631361, 1265011073, 2281701377, 9524994049, 52613349377, 73171503617, 106907803649, 212733001729, 289910292481, 2748779069441}; Table[Log[2, MultiplicativeOrder[10, p]], {p, A072982}]

CROSSREFS

Cf. A072982.

Sequence in context: A183197 A245459 A001368 * A196519 A184338 A184412

Adjacent sequences:  A197221 A197222 A197223 * A197225 A197226 A197227

KEYWORD

nonn,base,hard,more

AUTHOR

T. D. Noe, Oct 21 2011

EXTENSIONS

a(37)-a(39) from Ray Chandler, Nov 03 2011

STATUS

approved

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Last modified March 20 13:18 EDT 2019. Contains 321345 sequences. (Running on oeis4.)