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 | -3 |
| 4 | -3 |
| 5 | 17 |
| 6 | 45 |
| 7 | -90 |
| 8 | -546 |
| 9 | 130 |
| 10 | 5832 |
| 11 | 7074 |
| 12 | -53625 |
| 13 | -159214 |
| 14 | 374517 |
| 15 | 2419131 |
| 16 | -728364 |
| 17 | -30011530 |
| 18 | -37519884 |
| 19 | 307731042 |
| 20 | 940757526 |
| 21 | -2343385995 |
| 22 | -15421126275 |
| 23 | 5164279686 |
| 24 | 203045257272 |
| 25 | 255851517115 |
| 26 | -2186669342070 |
| 27 | -6760669947375 |
| 28 | 17391580425180 |