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 | 0 |
| 2 | 2 |
| 3 | 16 |
| 4 | 98 |
| 5 | 576 |
| 6 | 3362 |
| 7 | 19600 |
| 8 | 114242 |
| 9 | 665856 |
| 10 | 3880898 |
| 11 | 22619536 |
| 12 | 131836322 |
| 13 | 768398400 |
| 14 | 4478554082 |
| 15 | 26102926096 |
| 16 | 152139002498 |
| 17 | 886731088896 |
| 18 | 5168247530882 |
| 19 | 30122754096400 |
| 20 | 175568277047522 |
| 21 | 1023286908188736 |