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 | 1 |
| 3 | 4 |
| 4 | 27 |
| 5 | 232 |
| 6 | 2455 |
| 7 | 30852 |
| 8 | 449113 |
| 9 | 7432624 |
| 10 | 137829249 |
| 11 | 2830911220 |
| 12 | 63796168579 |
| 13 | 1565078980536 |
| 14 | 41521403685463 |
| 15 | 1184510408920468 |
| 16 | 36158133322895985 |
| 17 | 1176012432875399008 |
| 18 | 40599110984252798017 |
| 19 | 1482736219224857910756 |
| 20 | 57115359439245403771051 |