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 | 0 |
| 2 | 1 |
| 3 | -3 |
| 4 | 9 |
| 5 | -40 |
| 6 | 210 |
| 7 | -1176 |
| 8 | 7273 |
| 9 | -49932 |
| 10 | 372060 |
| 11 | -2971540 |
| 12 | 25359411 |
| 13 | -230364498 |
| 14 | 2215550428 |
| 15 | -22460391240 |
| 16 | 239236043985 |
| 17 | -2669869110856 |
| 18 | 31134833803728 |
| 19 | -378485082644400 |
| 20 | 4786085290280275 |
| 21 | -62838103267148790 |
| 22 | 855122923978737876 |