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 | -18 |
| 2 | 135 |
| 3 | -546 |
| 4 | 1413 |
| 5 | -3690 |
| 6 | 13230 |
| 7 | -40104 |
| 8 | 88452 |
| 9 | -211502 |
| 10 | 632259 |
| 11 | -1582488 |
| 12 | 3336198 |
| 13 | -8004366 |
| 14 | 20385711 |
| 15 | -45695742 |
| 16 | 98495865 |
| 17 | -224701146 |
| 18 | 511583207 |
| 19 | -1115983224 |
| 20 | 2374404237 |
| 21 | -5105519238 |
| 22 | 11129154192 |