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 | 6 |
| 3 | 24 |
| 4 | 94 |
| 5 | 378 |
| 6 | 1544 |
| 7 | 6380 |
| 8 | 26598 |
| 9 | 111658 |
| 10 | 471358 |
| 11 | 1998924 |
| 12 | 8509368 |
| 13 | 36341278 |
| 14 | 155634228 |
| 15 | 668116136 |
| 16 | 2874157222 |
| 17 | 12387209982 |
| 18 | 53475080494 |
| 19 | 231189987224 |
| 20 | 1000834283190 |
| 21 | 4337864724462 |
| 22 | 18821884379924 |
| 23 | 81748960355484 |
| 24 | 355383570351664 |
| 25 | 1546239230878154 |