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 | 1 |
| 2 | 0 |
| 3 | 3 |
| 4 | -1 |
| 5 | 25 |
| 6 | 59 |
| 7 | 721 |
| 8 | -841 |
| 9 | 60481 |
| 10 | 15119 |
| 11 | 3628801 |
| 12 | 12972959 |
| 13 | 479001601 |
| 14 | 8648639 |
| 15 | 134399865601 |
| 16 | -218205187201 |
| 17 | 20922789888001 |
| 18 | 174888473759999 |
| 19 | 6402373705728001 |
| 20 | -15205972772390401 |
| 21 | 3652732042831872001 |
| 22 | 14079294028799 |
| 23 | 1124000727777607680001 |