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 | -48 |
| 2 | 1104 |
| 3 | -16192 |
| 4 | 170064 |
| 5 | -1362336 |
| 6 | 8662720 |
| 7 | -44981376 |
| 8 | 195082320 |
| 9 | -721175536 |
| 10 | 2319457632 |
| 11 | -6631997376 |
| 12 | 17231109824 |
| 13 | -41469483552 |
| 14 | 93703589760 |
| 15 | -200343312768 |
| 16 | 407488018512 |
| 17 | -793229226336 |
| 18 | 1487286966928 |
| 19 | -2697825744960 |
| 20 | 4744779429216 |
| 21 | -8110465650176 |