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 | -9 |
| 3 | 48 |
| 4 | -288 |
| 5 | 1917 |
| 6 | -13563 |
| 7 | 99927 |
| 8 | -758079 |
| 9 | 5879757 |
| 10 | -46401705 |
| 11 | 371337021 |
| 12 | -3005974710 |
| 13 | 24568145019 |
| 14 | -202442064183 |
| 15 | 1679864383800 |
| 16 | -14024716370064 |
| 17 | 117715927282470 |
| 18 | -992725129013121 |
| 19 | 8407191323492226 |
| 20 | -71467963130581758 |
| 21 | 609605555349330009 |