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 | 1 |
| 2 | 3 |
| 3 | 12 |
| 4 | 63 |
| 5 | 447 |
| 6 | 4286 |
| 7 | 56185 |
| 8 | 1008317 |
| 9 | 24917676 |
| 10 | 849963761 |
| 11 | 40142633815 |
| 12 | 2633061525012 |
| 13 | 240207555735097 |
| 14 | 30578843349537575 |
| 15 | 5434894746337720676 |
| 16 | 1352812180415380719387 |
| 17 | 471689727423751377883607 |
| 18 | 230943183470327388401886858 |
| 19 | 158839247095790148049487792081 |
| 20 | 153694547774391577758847456894905 |