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 | -2 |
| 3 | 6 |
| 4 | -28 |
| 5 | 70 |
| 6 | -1446 |
| 7 | -22302 |
| 8 | -855032 |
| 9 | -33435486 |
| 10 | -1541257250 |
| 11 | -80299386706 |
| 12 | -4675923739764 |
| 13 | -300809006015466 |
| 14 | -21184444811987030 |
| 15 | -1620869900459370150 |
| 16 | -133878027649528854000 |
| 17 | -11872222666784936265342 |
| 18 | -1125045987661214982721602 |
| 19 | -113458738692543731877937418 |