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 | 0 |
| 2 | 1 |
| 3 | 0 |
| 4 | 1 |
| 5 | 4 |
| 6 | 25 |
| 7 | 197 |
| 8 | 2454 |
| 9 | 48201 |
| 10 | 1604016 |
| 11 | 93315450 |
| 12 | 9696046452 |
| 13 | 1822564897453 |
| 14 | 625839625866540 |
| 15 | 395787709599238772 |
| 16 | 464137745175250610865 |
| 17 | 1015091996575508453655611 |
| 18 | 4160447945769725861550193834 |
| 19 | 32088553211819016484736085677320 |
| 20 | 467409605282347770524641700949750858 |