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This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

A367821 a(n) = first exponent k such that n^k starts with 9 or -1 if n is a power of 10.

Table of values

n a(n)
1 -1
2 53
3 2
4 78
5 10
6 176
7 13
8 21
9 1
10 -1
11 24
12 25
13 26
14 34
15 17
16 39
17 13
18 39
19 25
20 53
21 3
22 32
23 11
24 21
25 5
26 12
27 37
28 29
29 41
30 2
31 2
32 89
33 25
34 15
35 11
36 88
37 7
38 12
39 5
40 78
41 13
42 8
43 11
44 45
45 3
46 3
47 55
48 22
49 13
50 10
51 24
52 60
53 11
54 15
55 4
56 4
57 37
58 17
59 22
60 176
61 14
62 5
63 5
64 26
65 43
66 39
67 6
68 6
69 25
70 13
71 7

List of values

[-1, 53, 2, 78, 10, 176, 13, 21, 1, -1, 24, 25, 26, 34, 17, 39, 13, 39, 25, 53, 3, 32, 11, 21, 5, 12, 37, 29, 41, 2, 2, 89, 25, 15, 11, 88, 7, 12, 5, 78, 13, 8, 11, 45, 3, 3, 55, 22, 13, 10, 24, 60, 11, 15, 4, 4, 37, 17, 22, 176, 14, 5, 5, 26, 43, 39, 6, 6, 25, 13, 7]

Started in 1964 by Neil J. A. Sloane | Maintained by The OEIS Foundation Inc.

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