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 | 0 |
| 3 | -1 |
| 4 | 2 |
| 5 | -4 |
| 6 | 16 |
| 7 | -120 |
| 8 | 1084 |
| 9 | -10568 |
| 10 | 111196 |
| 11 | -1269764 |
| 12 | 15728360 |
| 13 | -210510936 |
| 14 | 3029497472 |
| 15 | -46654106824 |
| 16 | 765497451536 |
| 17 | -13330741903360 |
| 18 | 245546485746064 |
| 19 | -4769321293582128 |
| 20 | 97417091239222336 |
| 21 | -2087367002843576384 |
| 22 | 46814167766826521920 |
| 23 | -1096698328458955351616 |