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) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 0 |
| 5 | 120 |
| 6 | 1800 |
| 7 | 16800 |
| 8 | 126000 |
| 9 | 834120 |
| 10 | 5102880 |
| 11 | 29607600 |
| 12 | 165526200 |
| 13 | 901020120 |
| 14 | 4808987400 |
| 15 | 25292030280 |
| 16 | 131542740000 |
| 17 | 678330198120 |
| 18 | 3474970629480 |
| 19 | 17710714165200 |
| 20 | 89904725757000 |