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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.

A274484 G.f. satisfies: A(x)^2 = A( x^2/(1 - 4*x + 2*x^2) ).

Table of values

n a(n)
1 1
2 2
3 6
4 20
5 71
6 262
7 994
8 3852
9 15183
10 60686
11 245410
12 1002300
13 4128448
14 17129920
15 71529800
16 300355184
17 1267386163
18 5371101382
19 22850230642
20 97546995260
21 417717017392
22 1793765580704
23 7722405668232
24 33323153856880
25 144099312039391
26 624347587536782
27 2710036186345914
28 11782865084403212
29 51310167663855675
30 223762749750806942
31 977155903597684074
32 4272633455348970588
33 18704696346822470087
34 81978422471165944654

List of values

[1, 2, 6, 20, 71, 262, 994, 3852, 15183, 60686, 245410, 1002300, 4128448, 17129920, 71529800, 300355184, 1267386163, 5371101382, 22850230642, 97546995260, 417717017392, 1793765580704, 7722405668232, 33323153856880, 144099312039391, 624347587536782, 2710036186345914, 11782865084403212, 51310167663855675, 223762749750806942, 977155903597684074, 4272633455348970588, 18704696346822470087, 81978422471165944654]

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