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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.

A187742 G.f.: Sum_{n>=0} (n+x)^n * x^n / (1 + n*x + x^2)^n.

Table of values

n a(n)
0 1
1 1
2 4
3 14
4 66
5 384
6 2640
7 20880
8 186480
9 1854720
10 20321280
11 243129600
12 3153427200
13 44068147200
14 660064204800
15 10548573235200
16 179151388416000
17 3222109642752000
18 61178237632512000
19 1222853377794048000
20 25667116186263552000
21 564433265896980480000
22 12977099311614197760000

List of values

[1, 1, 4, 14, 66, 384, 2640, 20880, 186480, 1854720, 20321280, 243129600, 3153427200, 44068147200, 660064204800, 10548573235200, 179151388416000, 3222109642752000, 61178237632512000, 1222853377794048000, 25667116186263552000, 564433265896980480000, 12977099311614197760000]

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

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