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 | 1 |
| 2 | 3 |
| 3 | 21 |
| 4 | 282 |
| 5 | 6210 |
| 6 | 202410 |
| 7 | 9135630 |
| 8 | 545007960 |
| 9 | 41514583320 |
| 10 | 3930730108200 |
| 11 | 452785322266200 |
| 12 | 62347376347779600 |
| 13 | 10112899541133589200 |
| 14 | 1908371363842760216400 |
| 15 | 414517594539154672566000 |
| 16 | 102681435747106627787376000 |
| 17 | 28772944645196614863048048000 |