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 | 1 |
| 3 | -4 |
| 4 | 11 |
| 5 | -20 |
| 6 | 18 |
| 7 | 29 |
| 8 | -192 |
| 9 | 609 |
| 10 | -1546 |
| 11 | 3526 |
| 12 | -7612 |
| 13 | 16043 |
| 14 | -33646 |
| 15 | 70811 |
| 16 | -149254 |
| 17 | 311978 |
| 18 | -637848 |
| 19 | 1256828 |
| 20 | -2349416 |
| 21 | 4083285 |
| 22 | -6371712 |
| 23 | 8192504 |
| 24 | -5904271 |
| 25 | -10617727 |
| 26 | 66446880 |
| 27 | -219604201 |
| 28 | 598613303 |
| 29 | -1479990203 |
| 30 | 3447208705 |
| 31 | -7716077651 |
| 32 | 16800683537 |
| 33 | -35877727580 |