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 | 1 |
| 3 | 1 |
| 4 | -3 |
| 5 | 5 |
| 6 | 1 |
| 7 | -39 |
| 8 | 117 |
| 9 | 13 |
| 10 | -1311 |
| 11 | 3441 |
| 12 | 9525 |
| 13 | -78603 |
| 14 | 16961 |
| 15 | 1520521 |
| 16 | -3649323 |
| 17 | -28760163 |
| 18 | 144787265 |
| 19 | 601582689 |
| 20 | -5374096875 |
| 21 | -15170850555 |
| 22 | 225456060897 |
| 23 | 461284881657 |
| 24 | -11141961064971 |
| 25 | -15963771799251 |
| 26 | 647040052660257 |
| 27 | 569313149887057 |