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 | 2 |
| 3 | 4 |
| 4 | 0 |
| 5 | -104 |
| 6 | -1200 |
| 7 | -10352 |
| 8 | -68992 |
| 9 | -177536 |
| 10 | 5310720 |
| 11 | 145374208 |
| 12 | 2512029696 |
| 13 | 33484862464 |
| 14 | 294806779904 |
| 15 | -1053894275072 |
| 16 | -133585065738240 |
| 17 | -4148745576218624 |
| 18 | -92116699894185984 |
| 19 | -1510783598900412416 |
| 20 | -11327731683300474880 |
| 21 | 414155615537321476096 |
| 22 | 25541948643911385219072 |