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 | 1 |
| 2 | -5 |
| 3 | 25 |
| 4 | -119 |
| 5 | 301 |
| 6 | 5611 |
| 7 | -171275 |
| 8 | 3574705 |
| 9 | -68597639 |
| 10 | 1282415131 |
| 11 | -23479249199 |
| 12 | 409082338105 |
| 13 | -6146707844315 |
| 14 | 46462772999371 |
| 15 | 2072826643602541 |
| 16 | -160983324879816479 |
| 17 | 8004468391727017585 |
| 18 | -352443295329194182085 |
| 19 | 14817357881274444545161 |