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 | 0 |
| 2 | 1 |
| 3 | 6 |
| 4 | 25 |
| 5 | 126 |
| 6 | 733 |
| 7 | 5086 |
| 8 | 40423 |
| 9 | 363262 |
| 10 | 3629743 |
| 11 | 39920638 |
| 12 | 479011993 |
| 13 | 6227066878 |
| 14 | 87178426333 |
| 15 | 1307675013118 |
| 16 | 20922791915023 |
| 17 | 355687438417918 |
| 18 | 6402373740187423 |
| 19 | 121645100594626558 |
| 20 | 2432902008831369073 |