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 | 2 |
| 3 | 6 |
| 4 | 24 |
| 5 | 120 |
| 6 | 720 |
| 7 | 5018 |
| 8 | 39374 |
| 9 | 337816 |
| 10 | 3092691 |
| 11 | 29659731 |
| 12 | 294107811 |
| 13 | 2988678546 |
| 14 | 30935695794 |
| 15 | 324832481490 |
| 16 | 3450158410649 |
| 17 | 36993206191004 |
| 18 | 399827092167771 |
| 19 | 4351269802153188 |