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 | 0 |
| 1 | 1 |
| 2 | 2 |
| 3 | 1 |
| 4 | -20 |
| 5 | -151 |
| 6 | -354 |
| 7 | 6217 |
| 8 | 100472 |
| 9 | 537777 |
| 10 | -7631270 |
| 11 | -223395919 |
| 12 | -2120164188 |
| 13 | 22050300505 |
| 14 | 1154262915638 |
| 15 | 17130776734905 |
| 16 | -105423782758544 |
| 17 | -11372993234072863 |
| 18 | -245877012220234446 |
| 19 | 345837436238423521 |
| 20 | 188329590656514108380 |