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 | 2 |
| 2 | 5 |
| 3 | 17 |
| 4 | 72 |
| 5 | 345 |
| 6 | 1773 |
| 7 | 9525 |
| 8 | 52788 |
| 9 | 299463 |
| 10 | 1730178 |
| 11 | 10144818 |
| 12 | 60211926 |
| 13 | 361042498 |
| 14 | 2183809018 |
| 15 | 13308564682 |
| 16 | 81637319641 |
| 17 | 503667864976 |
| 18 | 3123298907641 |
| 19 | 19456221197941 |
| 20 | 121696331095636 |
| 21 | 764008782313381 |