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 | -1 |
| 2 | 4 |
| 3 | -39 |
| 4 | 536 |
| 5 | -9115 |
| 6 | 185904 |
| 7 | -4461877 |
| 8 | 123647488 |
| 9 | -3886461081 |
| 10 | 136538590400 |
| 11 | -5300491027711 |
| 12 | 225313697972736 |
| 13 | -10409021924850211 |
| 14 | 519298241645107456 |
| 15 | -27824560148201248125 |
| 16 | 1593597443825288904704 |
| 17 | -97153909607626767338353 |
| 18 | 6281720886474120790582272 |