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) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 0 |
| 4 | -2 |
| 5 | 4 |
| 6 | 10 |
| 7 | -150 |
| 8 | 838 |
| 9 | 222 |
| 10 | -82616 |
| 11 | 1408364 |
| 12 | -13862308 |
| 13 | -18747672 |
| 14 | 5307622274 |
| 15 | -170657860276 |
| 16 | 3561218897884 |
| 17 | -33756455501714 |
| 18 | -1481233045213718 |
| 19 | 116803294574962288 |
| 20 | -5108843717328225572 |
| 21 | 157037998518149186728 |
| 22 | -1976107915155933805542 |