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) |
|---|---|
| 1 | 1 |
| 2 | -3 |
| 3 | 12 |
| 4 | -64 |
| 5 | 372 |
| 6 | -2268 |
| 7 | 14394 |
| 8 | -94296 |
| 9 | 632328 |
| 10 | -4317846 |
| 11 | 29925108 |
| 12 | -209966748 |
| 13 | 1488507931 |
| 14 | -10645680858 |
| 15 | 76717312932 |
| 16 | -556528367791 |
| 17 | 4060765734816 |
| 18 | -29782931545368 |
| 19 | 219444442931836 |
| 20 | -1623585342758532 |
| 21 | 12057148232386980 |
| 22 | -89842712017158526 |
| 23 | 671521130395037280 |