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) |
|---|---|
| 1 | -1 |
| 2 | 3 |
| 3 | -28 |
| 4 | 259 |
| 5 | -3126 |
| 6 | 46632 |
| 7 | -823544 |
| 8 | 16777475 |
| 9 | -387420517 |
| 10 | 9999996878 |
| 11 | -285311670612 |
| 12 | 8916100495144 |
| 13 | -302875106592254 |
| 14 | 11112006824734476 |
| 15 | -437893890380862528 |
| 16 | 18446744073726329091 |
| 17 | -827240261886336764178 |
| 18 | 39346408075296150201567 |