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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.

A201826 Central coefficients in Product_{k=1..n} (1 + k*y + y^2).

Table of values

n a(n)
0 1
1 1
2 4
3 18
4 100
5 660
6 5038
7 43624
8 422252
9 4516380
10 52885644
11 672781824
12 9238314358
13 136175455234
14 2144494356834
15 35930786795040
16 638168940129732
17 11976278012219556
18 236791150694618872
19 4919643784275283480
20 107152493449339765396
21 2441410548192907949196

List of values

[1, 1, 4, 18, 100, 660, 5038, 43624, 422252, 4516380, 52885644, 672781824, 9238314358, 136175455234, 2144494356834, 35930786795040, 638168940129732, 11976278012219556, 236791150694618872, 4919643784275283480, 107152493449339765396, 2441410548192907949196]

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

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