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 | -30 |
| 2 | 405 |
| 3 | -3250 |
| 4 | 17460 |
| 5 | -69456 |
| 6 | 237485 |
| 7 | -817830 |
| 8 | 2827605 |
| 9 | -8867120 |
| 10 | 25403229 |
| 11 | -73380060 |
| 12 | 215448665 |
| 13 | -595626330 |
| 14 | 1559581965 |
| 15 | -4136899912 |
| 16 | 11020769280 |
| 17 | -28085275230 |
| 18 | 69659708200 |
| 19 | -174426721890 |
| 20 | 433560026502 |