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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.

A268402 Number of North-East lattice paths from (0,0) to (n,n) that bounce off the diagonal y = x to the right exactly four times.

Table of values

n a(n)
5 1
6 7
7 40
8 204
9 977
10 4493
11 20091
12 88025
13 379766
14 1618898
15 6835636
16 28640302
17 119236085
18 493772409
19 2035611612
20 8359873866
21 34219553297
22 139672169795
23 568675783762
24 2310315996126
25 9367885987455
26 37920179012135
27 153263612914150
28 618611076034828
29 2493830719572639
30 10042451847789161

List of values

[1, 7, 40, 204, 977, 4493, 20091, 88025, 379766, 1618898, 6835636, 28640302, 119236085, 493772409, 2035611612, 8359873866, 34219553297, 139672169795, 568675783762, 2310315996126, 9367885987455, 37920179012135, 153263612914150, 618611076034828, 2493830719572639, 10042451847789161]

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

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