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 | 0 |
| 2 | -6 |
| 3 | -21 |
| 4 | -40 |
| 5 | -5 |
| 6 | 504 |
| 7 | 4697 |
| 8 | 39808 |
| 9 | 362151 |
| 10 | 3627800 |
| 11 | 39915469 |
| 12 | 478999872 |
| 13 | 6227018603 |
| 14 | 87178288456 |
| 15 | 1307674364625 |
| 16 | 20922789883904 |
| 17 | 355687428091087 |
| 18 | 6402373705722168 |
| 19 | 121645100408825141 |
| 20 | 2432902008176632000 |