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 | 0 |
| 2 | 4 |
| 3 | 4 |
| 4 | 52 |
| 5 | 164 |
| 6 | 1364 |
| 7 | 7620 |
| 8 | 60148 |
| 9 | 449252 |
| 10 | 3831700 |
| 11 | 33811716 |
| 12 | 320082228 |
| 13 | 3178774564 |
| 14 | 33234163668 |
| 15 | 363535920196 |
| 16 | 4153091085172 |
| 17 | 49406896240996 |
| 18 | 610777358429204 |
| 19 | 7830140410294148 |
| 20 | 103914148870277556 |
| 21 | 1425254885630973604 |
| 22 | 20173671034640405588 |