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) |
|---|---|
| 4 | 3 |
| 5 | 20 |
| 6 | 130 |
| 7 | 924 |
| 8 | 7308 |
| 9 | 64224 |
| 10 | 623376 |
| 11 | 6636960 |
| 12 | 76998240 |
| 13 | 967524480 |
| 14 | 13096736640 |
| 15 | 190060335360 |
| 16 | 2944310342400 |
| 17 | 48503818137600 |
| 18 | 846795372595200 |
| 19 | 15618926924697600 |
| 20 | 303517672703078400 |
| 21 | 6198400928176128000 |
| 22 | 132720966600284160000 |
| 23 | 2973385109386137600000 |