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 | -3 |
| 2 | 12 |
| 3 | -63 |
| 4 | 420 |
| 5 | -3435 |
| 6 | 33462 |
| 7 | -379155 |
| 8 | 4903896 |
| 9 | -71318259 |
| 10 | 1152202290 |
| 11 | -20474486043 |
| 12 | 396890715636 |
| 13 | -8334602179995 |
| 14 | 188486823883134 |
| 15 | -4567087352339235 |
| 16 | 118039115079323952 |
| 17 | -3241465018561379427 |
| 18 | 94249758656850366186 |
| 19 | -2892678859033260044043 |