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 | 4 |
| 2 | 28 |
| 3 | 216 |
| 4 | -2592 |
| 5 | -449280 |
| 6 | -42405120 |
| 7 | -4187635200 |
| 8 | -470931148800 |
| 9 | -61395115622400 |
| 10 | -9285015785472000 |
| 11 | -1621094541631488000 |
| 12 | -324607299684433920000 |
| 13 | -74032650725692538880000 |
| 14 | -19101781491742463754240000 |
| 15 | -5540523747380685884620800000 |