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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.

A131455 Number of inequivalent properly oriented and labeled planar chord diagrams whose associated planar tree is a path on n + 1 vertices.

Table of values

n a(n)
1 1
2 2
3 18
4 284
5 7280
6 273246
7 14144592
8 965491288
9 84027112704
10 9081387766810
11 1193283000239616
12 187340544144604212
13 34633340434838499328
14 7446726867419368499894
15 1842612127654047957411840
16 519870106084045866346942256
17 165896395346243470375430193152
18 59450668490817059243377908811698
19 23773400714993519201980928470155264

List of values

[1, 2, 18, 284, 7280, 273246, 14144592, 965491288, 84027112704, 9081387766810, 1193283000239616, 187340544144604212, 34633340434838499328, 7446726867419368499894, 1842612127654047957411840, 519870106084045866346942256, 165896395346243470375430193152, 59450668490817059243377908811698, 23773400714993519201980928470155264]

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

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