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 | -62 |
| 3 | -723 |
| 4 | -4072 |
| 5 | -15505 |
| 6 | -45936 |
| 7 | -112609 |
| 8 | -221824 |
| 9 | -168561 |
| 10 | 2628800 |
| 11 | 38145239 |
| 12 | 476015616 |
| 13 | 6222193991 |
| 14 | 87170761664 |
| 15 | 1307662977375 |
| 16 | 20922773110784 |
| 17 | 355687403958431 |
| 18 | 6402373671715776 |
| 19 | 121645100361786119 |
| 20 | 2432902008112640000 |