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 | -22 |
| 2 | 231 |
| 3 | -1562 |
| 4 | 7799 |
| 5 | -31438 |
| 6 | 109208 |
| 7 | -341660 |
| 8 | 987327 |
| 9 | -2672868 |
| 10 | 6848490 |
| 11 | -16752958 |
| 12 | 39388481 |
| 13 | -89439944 |
| 14 | 196910681 |
| 15 | -421739450 |
| 16 | 881199561 |
| 17 | -1800336692 |
| 18 | 3603535166 |
| 19 | -7078509064 |
| 20 | 13665905671 |