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 | 15 |
| 2 | -105 |
| 3 | 1575 |
| 4 | -29190 |
| 5 | 603225 |
| 6 | -13352850 |
| 7 | 309605625 |
| 8 | -7422255645 |
| 9 | 182481301800 |
| 10 | -4575894819300 |
| 11 | 116581172754375 |
| 12 | -3009161401332975 |
| 13 | 78523515330379875 |
| 14 | -2068113764887828875 |
| 15 | 54904020923799337500 |
| 16 | -1467692309121298737960 |
| 17 | 39472725372798507822900 |
| 18 | -1067296235915278105855650 |
| 19 | 28996357915496677935088125 |
| 20 | -791147023483262777604486675 |
| 21 | 21669197341488265510394307750 |