

A284602


Numbers n such that decimal representation of 1/n is either finite or has even period length.


2



1, 2, 4, 5, 7, 8, 10, 11, 13, 14, 16, 17, 19, 20, 21, 22, 23, 25, 26, 28, 29, 32, 33, 34, 35, 38, 39, 40, 42, 44, 46, 47, 49, 50, 51, 52, 55, 56, 57, 58, 59, 61, 63, 64, 65, 66, 68, 69, 70, 73, 76, 77, 78, 80, 84, 85, 87, 88, 89, 91, 92, 94, 95, 97, 98, 99, 100, 101, 102, 103, 104, 105, 109, 110, 112, 113, 114, 115
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OFFSET

1,2


COMMENTS

All numbers of the form 2^i*5^j with i, j >= 0 are in this sequence (numbers with a finite decimal expansion).
If k is in the sequence, then so are 2k and 5k.
Primitives: 1, 7, 11, 13, 17, 19, 21, 23, 29, 33, 39, 47, 49, 51, 57, 59, 61, 63, ..., .
(End)


LINKS



EXAMPLE

14 is in the sequence because 1/14 = 0.0714285(714285)... length of the period 6, 6 is even.


MATHEMATICA

Select[Range[115], Mod[Length[RealDigits[1/#][[1, 1]]], 2] == 0 & ]


CROSSREFS



KEYWORD

nonn,base


AUTHOR



STATUS

approved



