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 | 0 |
| 2 | 1 |
| 3 | 5 |
| 4 | 11 |
| 5 | -203 |
| 6 | -17207 |
| 7 | -3607 |
| 8 | 1408301 |
| 9 | 8181503 |
| 10 | -3299598169 |
| 11 | -14983154641 |
| 12 | -449428440959 |
| 13 | 2480887997789 |
| 14 | 19076621521399973 |
| 15 | -31806561859970819 |
| 16 | -3485566370059659659 |
| 17 | -2180443004193000007 |
| 18 | 54188073629843061671671 |