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 | 0 |
| 3 | 1 |
| 4 | 0 |
| 5 | 3 |
| 6 | -24 |
| 7 | 61 |
| 8 | -256 |
| 9 | 1383 |
| 10 | -5632 |
| 11 | 28345 |
| 12 | -156032 |
| 13 | 808299 |
| 14 | -4761600 |
| 15 | 28955317 |
| 16 | -178225152 |
| 17 | 1188919631 |
| 18 | -8081772544 |
| 19 | 56978370417 |
| 20 | -422364381184 |
| 21 | 3196912985683 |
| 22 | -25184814366720 |
| 23 | 205147130407981 |
| 24 | -1713906141986816 |