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 | 1 |
| 3 | 11 |
| 4 | 38 |
| 5 | 274 |
| 6 | 2844 |
| 7 | 21888 |
| 8 | 231888 |
| 9 | 2580912 |
| 10 | 37879200 |
| 11 | 459884160 |
| 12 | 7372650240 |
| 13 | 112624905600 |
| 14 | 2002334100480 |
| 15 | 37047155846400 |
| 16 | 721997863372800 |
| 17 | 14458523340441600 |
| 18 | 320885263596441600 |
| 19 | 7222523219238297600 |
| 20 | 172441642330718208000 |
| 21 | 4367517061604788224000 |