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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.

A102693 a(n) is the number of digraphs (not allowing loops) with vertices 1,2,...,n that have a unique Eulerian tour (up to cyclic shift).

Table of values

n a(n)
2 1
3 5
4 42
5 504
6 7920
7 154440
8 3603600
9 98017920
10 3047466240
11 106661318400
12 4151586700800
13 177925144320000
14 8326896754176000
15 422590010274432000
16 23118159385601280000
17 1356265350621941760000
18 84945040381058457600000
19 5657339689378493276160000

List of values

[1, 5, 42, 504, 7920, 154440, 3603600, 98017920, 3047466240, 106661318400, 4151586700800, 177925144320000, 8326896754176000, 422590010274432000, 23118159385601280000, 1356265350621941760000, 84945040381058457600000, 5657339689378493276160000]

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

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