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 | 0 |
| 3 | -3 |
| 4 | 16 |
| 5 | -75 |
| 6 | 336 |
| 7 | -1295 |
| 8 | 1632 |
| 9 | 55881 |
| 10 | -1124000 |
| 11 | 16722981 |
| 12 | -229985040 |
| 13 | 3089923837 |
| 14 | -41225160144 |
| 15 | 545880027225 |
| 16 | -7069180940864 |
| 17 | 86130735547665 |
| 18 | -882387869940288 |
| 19 | 3847692639294541 |
| 20 | 171852333163131600 |
| 21 | -8392137456287472699 |
| 22 | 276055495385982856720 |
| 23 | -8067943451470397940543 |