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 | 0 |
| 2 | 2 |
| 3 | -1 |
| 4 | 5 |
| 5 | -11 |
| 6 | 36 |
| 7 | -107 |
| 8 | 311 |
| 9 | -850 |
| 10 | 2208 |
| 11 | -5519 |
| 12 | 13566 |
| 13 | -33562 |
| 14 | 84937 |
| 15 | -220307 |
| 16 | 579413 |
| 17 | -1522616 |
| 18 | 3954016 |
| 19 | -10100863 |
| 20 | 25416877 |
| 21 | -63324271 |
| 22 | 157248035 |
| 23 | -391478354 |
| 24 | 980410093 |
| 25 | -2470810086 |
| 26 | 6253495883 |
| 27 | -15846525758 |
| 28 | 40093721908 |
| 29 | -101116823798 |
| 30 | 254093749587 |
| 31 | -636547773777 |