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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.

A151332 Number of walks within N^2 (the first quadrant of Z^2) starting and ending at (0,0) and consisting of 4 n steps taken from {(-1, -1), (-1, 1), (1, 0)}.

Table of values

n a(n)
0 1
1 2
2 28
3 660
4 20020
5 705432
6 27457584
7 1147334760
8 50561468100
9 2322279359400
10 110250966574320
11 5377893986141040
12 268315541493159888
13 13645106597301720800
14 705378072079232798400
15 36985702814877062972880
16 1963555139681260758978660
17 105393959626252993455319560

List of values

[1, 2, 28, 660, 20020, 705432, 27457584, 1147334760, 50561468100, 2322279359400, 110250966574320, 5377893986141040, 268315541493159888, 13645106597301720800, 705378072079232798400, 36985702814877062972880, 1963555139681260758978660, 105393959626252993455319560]

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

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