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 | 1 |
| 3 | 3 |
| 4 | 7 |
| 5 | 21 |
| 6 | 75 |
| 7 | 257 |
| 8 | 930 |
| 9 | 3104 |
| 10 | 9265 |
| 11 | 21304 |
| 12 | 81392 |
| 13 | 139612 |
| 14 | 427454 |
| 15 | 1176912 |
| 16 | 2491134 |
| 17 | 4319362 |
| 18 | 16243200 |
| 19 | 21965930 |
| 20 | 76738851 |
| 21 | 158374741 |