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.
| n | a(n) |
|---|---|
| 3 | 1 |
| 4 | 31 |
| 5 | 602 |
| 6 | 10206 |
| 7 | 166824 |
| 8 | 2739240 |
| 9 | 46070640 |
| 10 | 801496080 |
| 11 | 14495120640 |
| 12 | 273158645760 |
| 13 | 5368729766400 |
| 14 | 110055327782400 |
| 15 | 2351983118284800 |
| 16 | 52361635508582400 |
| 17 | 1213240925049753600 |
| 18 | 29227769646147072000 |
| 19 | 731310069474496512000 |
| 20 | 18984684514588176384000 |