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 | 0 |
| 1 | 1 |
| 2 | 1 |
| 3 | 25 |
| 4 | 337 |
| 5 | 4321 |
| 6 | 46681 |
| 7 | 437305 |
| 8 | 3721537 |
| 9 | 29740561 |
| 10 | 228000361 |
| 11 | 1699890985 |
| 12 | 12435686737 |
| 13 | 89792976001 |
| 14 | 642488104441 |
| 15 | 4567920215065 |
| 16 | 32331017955937 |
| 17 | 228106608326641 |
| 18 | 1605738151030921 |
| 19 | 11285298643841545 |
| 20 | 79223419486529137 |