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 | 0 |
| 1 | 1 |
| 2 | 1 |
| 3 | 1 |
| 4 | 9 |
| 5 | 45 |
| 6 | 237 |
| 7 | 1335 |
| 8 | 7767 |
| 9 | 45867 |
| 10 | 275865 |
| 11 | 1681776 |
| 12 | 10373614 |
| 13 | 64620952 |
| 14 | 405996375 |
| 15 | 2569673028 |
| 16 | 16369919346 |
| 17 | 104880810464 |
| 18 | 675383823982 |
| 19 | 4368948815362 |
| 20 | 28377658731830 |
| 21 | 185003199176340 |
| 22 | 1210146671320603 |
| 23 | 7940083938945628 |
| 24 | 52243075940256372 |