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 | 0 |
| 4 | 2 |
| 5 | 8 |
| 6 | -64 |
| 7 | -112 |
| 8 | 2064 |
| 9 | 8192 |
| 10 | -157056 |
| 11 | -599808 |
| 12 | 16072704 |
| 13 | 80010240 |
| 14 | -2484268032 |
| 15 | -13537247232 |
| 16 | 506459129856 |
| 17 | 3160676007936 |
| 18 | -135526008225792 |
| 19 | -929451393220608 |
| 20 | 45507663438741504 |
| 21 | 343173318976733184 |
| 22 | -18834884514478817280 |
| 23 | -154043745649772986368 |