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 | -1 |
| 3 | 1 |
| 4 | -7 |
| 5 | -49 |
| 6 | -1191 |
| 7 | -31569 |
| 8 | -1051695 |
| 9 | -41520593 |
| 10 | -1896894223 |
| 11 | -98362962257 |
| 12 | -5705059841823 |
| 13 | -365846227736001 |
| 14 | -25696840682622175 |
| 15 | -1961769357361345473 |
| 16 | -161728572333727674687 |
| 17 | -14318505129615014956737 |
| 18 | -1354916705432679538845759 |
| 19 | -136467389971873491004759617 |