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) |
|---|---|
| 1 | 0 |
| 2 | 1 |
| 3 | 2 |
| 4 | 3 |
| 5 | 7 |
| 6 | 25 |
| 7 | 126 |
| 8 | 968 |
| 9 | 11752 |
| 10 | 240615 |
| 11 | 8529544 |
| 12 | 534168034 |
| 13 | 59794030430 |
| 14 | 12082250628276 |
| 15 | 4446033336286696 |
| 16 | 3002923486915259644 |
| 17 | 3748228681583390913192 |
| 18 | 8696890616699403375722774 |
| 19 | 37700601714008218904828607832 |
| 20 | 306674623374061557486512987705844 |