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 | 1 |
| 3 | 0 |
| 4 | -4 |
| 5 | 64 |
| 6 | -240 |
| 7 | -2656 |
| 8 | 15360 |
| 9 | -88064 |
| 10 | -1714176 |
| 11 | -28506112 |
| 12 | 59061248 |
| 13 | 1975595008 |
| 14 | -107448238080 |
| 15 | 858018086912 |
| 16 | 12209125720064 |
| 17 | 61138306793472 |
| 18 | -297002777247744 |
| 19 | -7586668200067072 |
| 20 | 309144292445913088 |
| 21 | -20518123014457393152 |
| 22 | -58844751529044344832 |
| 23 | 2248491526894557069312 |