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) |
|---|---|
| 0 | 1 |
| 1 | 21 |
| 2 | 336 |
| 3 | 5040 |
| 4 | 75600 |
| 5 | 1164240 |
| 6 | 18627840 |
| 7 | 311351040 |
| 8 | 5448643200 |
| 9 | 99891792000 |
| 10 | 1917922406400 |
| 11 | 38532804710400 |
| 12 | 809188898918400 |
| 13 | 17739910476288000 |
| 14 | 405483668029440000 |
| 15 | 9650511299100672000 |