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A326818 a(n) is the smallest k such that the first significant digits of 1/k coincide with n. 1
1, 4, 3, 21, 2, 15, 13, 12, 11, 1, 9, 8, 72, 7, 63, 6, 56, 53, 51, 5, 46, 44, 42, 41, 4, 38, 36, 35, 34, 33, 32, 31, 3, 29, 28, 271, 27, 26, 251, 25, 24, 233, 23, 223, 22, 213, 21, 205, 201, 2, 193, 19, 186, 182, 18, 176, 173, 17, 167, 164, 162, 16, 157, 154, 152 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

This sequence differs from A052039 in how it treats reciprocals with terminating representation, i.e., the values 1/k for integers k whose prime factors are 2 and/or 5. For example, here we assume 1/5 = 0.2000... which leads to a(20) = 5, while in A052039 we consider 1/5 = 0.2 (without trailing zeros), which leads to A052039(20) = 48 instead.

LINKS

Table of n, a(n) for n=1..65.

EXAMPLE

a(123) = 81 because 1/81 = 0.0(123)4... and 81 is the smallest number with this property.

MATHEMATICA

a[n_] := Block[{d = IntegerDigits[n], m, k = 1}, m = Length[d]; While[ RealDigits[1/k, 10, m][[1]] != d, k++]; k]; Array[a, 65]

CROSSREFS

Cf. A052039, A034057.

Sequence in context: A281042 A076589 A275679 * A259229 A052039 A243661

Adjacent sequences:  A326815 A326816 A326817 * A326819 A326820 A326821

KEYWORD

nonn,base

AUTHOR

Giovanni Resta, Oct 20 2019

STATUS

approved

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Last modified June 25 03:59 EDT 2022. Contains 354835 sequences. (Running on oeis4.)