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 | 3 |
| 2 | 12 |
| 3 | 66 |
| 4 | 504 |
| 5 | 5040 |
| 6 | 60840 |
| 7 | 839160 |
| 8 | 12882240 |
| 9 | 217607040 |
| 10 | 4018896000 |
| 11 | 80691811200 |
| 12 | 1750850640000 |
| 13 | 40809559190400 |
| 14 | 1016150162227200 |
| 15 | 26898872647046400 |
| 16 | 753882642267955200 |
| 17 | 22291971504503500800 |
| 18 | 693356807039126630400 |