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 | 8 |
| 4 | 70 |
| 5 | 156 |
| 6 | 2982 |
| 7 | 19296 |
| 8 | 216396 |
| 9 | 917480 |
| 10 | 47847580 |
| 11 | 250815120 |
| 12 | 18724750980 |
| 13 | 116905717320 |
| 14 | 788402337660 |
| 15 | 11422960203648 |
| 16 | 1503958432951464 |
| 17 | 12400297557081840 |
| 18 | 2060467159019459400 |
| 19 | 19050402239258292000 |
| 20 | 185663459342909159640 |
| 21 | 1902329957427442126320 |