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 | 4 |
| 2 | 22 |
| 3 | 128 |
| 4 | 777 |
| 5 | 4872 |
| 6 | 31330 |
| 7 | 205560 |
| 8 | 1370868 |
| 9 | 9266104 |
| 10 | 63343006 |
| 11 | 437183260 |
| 12 | 3042337215 |
| 13 | 21323543252 |
| 14 | 150395596016 |
| 15 | 1066637271424 |
| 16 | 7602188660799 |
| 17 | 54422262148632 |
| 18 | 391146728466980 |
| 19 | 2821396586367568 |
| 20 | 20417766975784066 |
| 21 | 148200184917042112 |