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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.

A189912 Extended Motzkin numbers, Sum_{k>=0} C(n,k)*C(k), where C(k) is the extended Catalan number A057977(k).

Table of values

n a(n)
0 1
1 2
2 4
3 10
4 25
5 66
6 177
7 484
8 1339
9 3742
10 10538
11 29866
12 85087
13 243478
14 699324
15 2015082
16 5822619
17 16865718
18 48958404
19 142390542
20 414837699
21 1210439958
22 3536809521
23 10347314544
24 30306977757
25 88861597426
26 260798283502
27 766092871654
28 2252240916665

List of values

[1, 2, 4, 10, 25, 66, 177, 484, 1339, 3742, 10538, 29866, 85087, 243478, 699324, 2015082, 5822619, 16865718, 48958404, 142390542, 414837699, 1210439958, 3536809521, 10347314544, 30306977757, 88861597426, 260798283502, 766092871654, 2252240916665]

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

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