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 | 18 |
| 4 | 136 |
| 5 | 1625 |
| 6 | 23436 |
| 7 | 412972 |
| 8 | 8390656 |
| 9 | 193739769 |
| 10 | 5000050000 |
| 11 | 142656721086 |
| 12 | 4458051717120 |
| 13 | 151437584670385 |
| 14 | 5556003465485760 |
| 15 | 218946946471875000 |
| 16 | 9223372039002259456 |
| 17 | 413620131002462320337 |
| 18 | 19673204037747448432896 |
| 19 | 989209827833222327690890 |