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 | 1 |
| 3 | -3 |
| 4 | -3 |
| 5 | 25 |
| 6 | 25 |
| 7 | -223 |
| 8 | -223 |
| 9 | 2217 |
| 10 | 2217 |
| 11 | -23427 |
| 12 | -23427 |
| 13 | 258417 |
| 14 | 258417 |
| 15 | -2941311 |
| 16 | -2941311 |
| 17 | 34289041 |
| 18 | 34289041 |
| 19 | -407344771 |
| 20 | -407344771 |
| 21 | 4913508489 |
| 22 | 4913508489 |
| 23 | -60018592735 |
| 24 | -60018592735 |
| 25 | 740910077497 |
| 26 | 740910077497 |
| 27 | -9228860168451 |
| 28 | -9228860168451 |
| 29 | 115849095339489 |
| 30 | 115849095339489 |