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 | 1 |
| 2 | 5 |
| 3 | 13 |
| 4 | 45 |
| 5 | 121 |
| 6 | 413 |
| 7 | 1261 |
| 8 | 4221 |
| 9 | 13801 |
| 10 | 46365 |
| 11 | 155497 |
| 12 | 527613 |
| 13 | 1792805 |
| 14 | 6126293 |
| 15 | 20986153 |
| 16 | 72121853 |
| 17 | 248396793 |
| 18 | 857416949 |
| 19 | 2964896877 |
| 20 | 10269596445 |
| 21 | 35622421561 |
| 22 | 123728022269 |
| 23 | 430254861945 |
| 24 | 1497796774077 |
| 25 | 5219231003621 |