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 | -3 |
| 3 | 21 |
| 4 | -225 |
| 5 | 3207 |
| 6 | -56821 |
| 7 | 1202099 |
| 8 | -29558466 |
| 9 | 828401462 |
| 10 | -26068940938 |
| 11 | 910286433318 |
| 12 | -34930741605414 |
| 13 | 1461245816594058 |
| 14 | -66187658069563710 |
| 15 | 3227353484661602866 |
| 16 | -168557942284281821933 |
| 17 | 9388117645333487820387 |
| 18 | -555463036269652132509113 |