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 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 0 |
| 5 | 0 |
| 6 | 0 |
| 7 | 0 |
| 8 | 5040 |
| 9 | 362880 |
| 10 | 18144000 |
| 11 | 804988800 |
| 12 | 34488115200 |
| 13 | 1482082842240 |
| 14 | 65120246231040 |
| 15 | 2955402450000000 |
| 16 | 139297568464454400 |
| 17 | 6837892496270035200 |
| 18 | 350034595015623598080 |
| 19 | 18692451288585606954240 |
| 20 | 1041114148173066240000000 |