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 | 2 |
| 1 | 20 |
| 2 | 252 |
| 3 | 3432 |
| 4 | 48620 |
| 5 | 705432 |
| 6 | 10400600 |
| 7 | 155117520 |
| 8 | 2333606220 |
| 9 | 35345263800 |
| 10 | 538257874440 |
| 11 | 8233430727600 |
| 12 | 126410606437752 |
| 13 | 1946939425648112 |
| 14 | 30067266499541040 |
| 15 | 465428353255261088 |
| 16 | 7219428434016265740 |