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 | 1 |
| 4 | 0 |
| 5 | -4 |
| 6 | 14 |
| 7 | -30 |
| 8 | 33 |
| 9 | 55 |
| 10 | -429 |
| 11 | 1365 |
| 12 | -2652 |
| 13 | 1428 |
| 14 | 12920 |
| 15 | -64600 |
| 16 | 178296 |
| 17 | -277932 |
| 18 | -152950 |
| 19 | 2770350 |
| 20 | -10785390 |
| 21 | 25312650 |
| 22 | -26053020 |
| 23 | -84847620 |
| 24 | 576753450 |
| 25 | -1856900682 |
| 26 | 3566658438 |
| 27 | -843350102 |
| 28 | -24973594296 |
| 29 | 117328602840 |
| 30 | -317641049880 |
| 31 | 455822225496 |