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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.

A199923 a(n) = Sum_{k=0..3^(n-1)} gcd(k,3^(n-1)) for n > 0 and a(0) = 1.

Table of values

n a(n)
0 1
1 2
2 8
3 30
4 108
5 378
6 1296
7 4374
8 14580
9 48114
10 157464
11 511758
12 1653372
13 5314410
14 17006112
15 54206982
16 172186884
17 545258466
18 1721868840
19 5423886846
20 17046501516
21 53464027482
22 167365651248
23 523017660150
24 1631815099668
25 5083731656658
26 15816054042936

List of values

[1, 2, 8, 30, 108, 378, 1296, 4374, 14580, 48114, 157464, 511758, 1653372, 5314410, 17006112, 54206982, 172186884, 545258466, 1721868840, 5423886846, 17046501516, 53464027482, 167365651248, 523017660150, 1631815099668, 5083731656658, 15816054042936]

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

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