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 | 3 |
| 3 | -11 |
| 4 | 45 |
| 5 | -197 |
| 6 | 903 |
| 7 | -4279 |
| 8 | 20793 |
| 9 | -103049 |
| 10 | 518859 |
| 11 | -2646723 |
| 12 | 13648869 |
| 13 | -71039373 |
| 14 | 372693519 |
| 15 | -1968801519 |
| 16 | 10463578353 |
| 17 | -55909013009 |
| 18 | 300159426963 |
| 19 | -1618362158587 |
| 20 | 8759309660445 |
| 21 | -47574827600981 |
| 22 | 259215937709463 |
| 23 | -1416461675464871 |
| 24 | 7760733824437545 |
| 25 | -42624971294485657 |