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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.

A131428 a(n) = 2*C(n) - 1, where C(n) = A000108(n) are the Catalan numbers.

Table of values

n a(n)
0 1
1 1
2 3
3 9
4 27
5 83
6 263
7 857
8 2859
9 9723
10 33591
11 117571
12 416023
13 1485799
14 5348879
15 19389689
16 70715339
17 259289579
18 955277399
19 3534526379
20 13128240839
21 48932534039
22 182965127279
23 686119227299
24 2579808294647
25 9723892802903
26 36734706144303
27 139067101832007

List of values

[1, 1, 3, 9, 27, 83, 263, 857, 2859, 9723, 33591, 117571, 416023, 1485799, 5348879, 19389689, 70715339, 259289579, 955277399, 3534526379, 13128240839, 48932534039, 182965127279, 686119227299, 2579808294647, 9723892802903, 36734706144303, 139067101832007]

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

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