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 | 2 |
| 3 | 9 |
| 4 | 52 |
| 5 | 365 |
| 6 | 3006 |
| 7 | 28357 |
| 8 | 301064 |
| 9 | 3549177 |
| 10 | 45965530 |
| 11 | 648352001 |
| 12 | 9888877692 |
| 13 | 162112109029 |
| 14 | 2841669616982 |
| 15 | 53025262866045 |
| 16 | 1049180850990736 |
| 17 | 21937381717388657 |
| 18 | 483239096122434354 |
| 19 | 11184035897992673017 |
| 20 | 271287473871771163460 |
| 21 | 6881656485607798743261 |