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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.

A274478 G.f. satisfies: A(x)^2 = A( x^2/(1 - 2*x - 2*x^2) ).

Table of values

n a(n)
1 1
2 1
3 3
4 7
5 20
6 56
7 166
8 498
9 1530
10 4762
11 15022
12 47862
13 153859
14 498239
15 1623779
16 5321059
17 17520994
18 57937106
19 192304222
20 640446358
21 2139414409
22 7166431909
23 24065926653
24 81003492725
25 273229977460
26 923438683996
27 3126674842896
28 10604713671208
29 36025426127382
30 122566140787390
31 417584644921806
32 1424610537707166
33 4866239784751346
34 16642071212737394
35 56978489024931038
36 195289731964727862
37 670023314236521396
38 2301024202252503308
39 7909580344156028160

List of values

[1, 1, 3, 7, 20, 56, 166, 498, 1530, 4762, 15022, 47862, 153859, 498239, 1623779, 5321059, 17520994, 57937106, 192304222, 640446358, 2139414409, 7166431909, 24065926653, 81003492725, 273229977460, 923438683996, 3126674842896, 10604713671208, 36025426127382, 122566140787390, 417584644921806, 1424610537707166, 4866239784751346, 16642071212737394, 56978489024931038, 195289731964727862, 670023314236521396, 2301024202252503308, 7909580344156028160]

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