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 | 11 |
| 4 | 56 |
| 5 | 348 |
| 6 | 2578 |
| 7 | 22054 |
| 8 | 213798 |
| 9 | 2313638 |
| 10 | 27627434 |
| 11 | 360646314 |
| 12 | 5107177312 |
| 13 | 77954299144 |
| 14 | 1275489929604 |
| 15 | 22265845018412 |
| 16 | 412989204564572 |
| 17 | 8109686585668956 |
| 18 | 168051656468233972 |
| 19 | 3664479286118269972 |
| 20 | 83868072451846938336 |
| 21 | 2009964340465840802576 |