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 | 2 |
| 2 | 5 |
| 3 | 15 |
| 4 | 45 |
| 5 | 135 |
| 6 | 421 |
| 7 | 1466 |
| 8 | 5403 |
| 9 | 19417 |
| 10 | 69205 |
| 11 | 249569 |
| 12 | 883285 |
| 13 | 3024282 |
| 14 | 10359274 |
| 15 | 37010151 |
| 16 | 138333876 |
| 17 | 524680726 |
| 18 | 1964881580 |
| 19 | 7214899381 |
| 20 | 26104002605 |
| 21 | 93449335588 |
| 22 | 331875353107 |
| 23 | 1177784053061 |
| 24 | 4229817098432 |
| 25 | 15554800422055 |