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 | 4 |
| 2 | 33 |
| 3 | 303 |
| 4 | 2670 |
| 5 | 23741 |
| 6 | 222638 |
| 7 | 2211826 |
| 8 | 22325173 |
| 9 | 220321667 |
| 10 | 2128051302 |
| 11 | 20606839279 |
| 12 | 203631013986 |
| 13 | 2048538361591 |
| 14 | 20655036405780 |
| 15 | 205672896661755 |
| 16 | 2012878671315492 |
| 17 | 19505453673514959 |
| 18 | 190027534666354756 |
| 19 | 1884928265282803982 |
| 20 | 19032829919297816897 |
| 21 | 193085599933330233795 |