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 | 0 |
| 2 | 0 |
| 3 | -1 |
| 4 | 5 |
| 5 | -19 |
| 6 | 67 |
| 7 | -232 |
| 8 | 804 |
| 9 | -2806 |
| 10 | 9878 |
| 11 | -35072 |
| 12 | 125512 |
| 13 | -452388 |
| 14 | 1641028 |
| 15 | -5986993 |
| 16 | 21954973 |
| 17 | -80884423 |
| 18 | 299233543 |
| 19 | -1111219333 |
| 20 | 4140813373 |
| 21 | -15478839553 |
| 22 | 58028869153 |
| 23 | -218123355523 |
| 24 | 821908275547 |
| 25 | -3104046382351 |
| 26 | 11747506651599 |
| 27 | -44546351423299 |
| 28 | 169227201341651 |