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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.

A104184 a(n) is the number of paths from (0,0) to (n,0) using steps of the form (1,2),(1,1),(1,0),(1,-1) or (1,-2) and staying above the x-axis. Also, a(n) is the number of possible combinations of balls on the lawn after n turns, using a Motzkin variation of the (4,2)-case of the tennis ball problem considered by D. Merlini, R. Sprugnoli and M. C. Verri.

Table of values

n a(n)
0 1
1 1
2 3
3 9
4 32
5 120
6 473
7 1925
8 8034
9 34188
10 147787
11 647141
12 2864508
13 12796238
14 57615322
15 261197436
16 1191268350
17 5462080688
18 25162978925
19 116414836445
20 540648963645
21 2519574506595
22 11779011525030
23 55225888341334
24 259612579655392
25 1223396051745310

List of values

[1, 1, 3, 9, 32, 120, 473, 1925, 8034, 34188, 147787, 647141, 2864508, 12796238, 57615322, 261197436, 1191268350, 5462080688, 25162978925, 116414836445, 540648963645, 2519574506595, 11779011525030, 55225888341334, 259612579655392, 1223396051745310]

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

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