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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.

A263173 Number of Dyck paths of semilength n having exactly two (possibly overlapping) DUDU's (with U=(1,1), D=(1,-1)).

Table of values

n a(n)
4 1
5 3
6 15
7 58
8 231
9 891
10 3403
11 12870
12 48318
13 180356
14 670014
15 2479302
16 9143885
17 33627777
18 123366789
19 451612846
20 1650111453
21 6019100025
22 21922936343
23 79740801036
24 289690000380
25 1051250045960
26 3811012240380
27 13802994382860
28 49950211130905
29 180617997397887

List of values

[1, 3, 15, 58, 231, 891, 3403, 12870, 48318, 180356, 670014, 2479302, 9143885, 33627777, 123366789, 451612846, 1650111453, 6019100025, 21922936343, 79740801036, 289690000380, 1051250045960, 3811012240380, 13802994382860, 49950211130905, 180617997397887]

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

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