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 | 2 |
| 2 | 2 |
| 3 | -6 |
| 4 | -30 |
| 5 | 42 |
| 6 | 882 |
| 7 | 954 |
| 8 | -39870 |
| 9 | -203958 |
| 10 | 2300562 |
| 11 | 29677914 |
| 12 | -120958110 |
| 13 | -4657703958 |
| 14 | -7059175758 |
| 15 | 807984602874 |
| 16 | 6667870853250 |
| 17 | -145556787011958 |
| 18 | -2827006784652078 |
| 19 | 21703953751815834 |
| 20 | 1108558810703202210 |