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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.

A243872 Number of Dyck paths of semilength n having exactly 2 (possibly overlapping) occurrences of the consecutive steps UDUUUDDDUD (with U=(1,1), D=(1,-1)).

Table of values

n a(n)
9 1
10 4
11 16
12 65
13 263
14 1077
15 4419
16 18132
17 74368
18 304778
19 1247972
20 5105477
21 20867862
22 85219608
23 347724794
24 1417697157
25 5775652743
26 23512922998
27 95657223246
28 388912046916
29 1580241458120
30 6417249216667
31 26046042351889
32 105661066012240
33 428430870576913

List of values

[1, 4, 16, 65, 263, 1077, 4419, 18132, 74368, 304778, 1247972, 5105477, 20867862, 85219608, 347724794, 1417697157, 5775652743, 23512922998, 95657223246, 388912046916, 1580241458120, 6417249216667, 26046042351889, 105661066012240, 428430870576913]

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

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