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 | 1 |
| 2 | 2 |
| 3 | 9 |
| 4 | 32 |
| 5 | 250 |
| 6 | 864 |
| 7 | 12348 |
| 8 | 67584 |
| 9 | 804816 |
| 10 | 5760000 |
| 11 | 116915040 |
| 12 | 686776320 |
| 13 | 19323757440 |
| 14 | 157991178240 |
| 15 | 2951575200000 |
| 16 | 42301705420800 |
| 17 | 1202482800691200 |
| 18 | 10048607738265600 |
| 19 | 425162773111910400 |
| 20 | 4541227794432000000 |