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 | 0 |
| 2 | -2 |
| 3 | -6 |
| 4 | -2 |
| 5 | 90 |
| 6 | 598 |
| 7 | 1554 |
| 8 | -10082 |
| 9 | -164310 |
| 10 | -1101242 |
| 11 | -1496286 |
| 12 | 64767118 |
| 13 | 965876730 |
| 14 | 7104497398 |
| 15 | 57428274 |
| 16 | -856472198402 |
| 17 | -14195316779190 |
| 18 | -122409183339482 |
| 19 | 25272908324034 |
| 20 | 21770258523698158 |