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 | -2 |
| 2 | 0 |
| 3 | 16 |
| 4 | -56 |
| 5 | 48 |
| 6 | 384 |
| 7 | -1920 |
| 8 | 3168 |
| 9 | 8512 |
| 10 | -66560 |
| 11 | 161280 |
| 12 | 113920 |
| 13 | -2224640 |
| 14 | 7311360 |
| 15 | -3354624 |
| 16 | -69253632 |
| 17 | 306754560 |
| 18 | -408059904 |
| 19 | -1898029056 |
| 20 | 12054196224 |
| 21 | -25377005568 |
| 22 | -38874316800 |
| 23 | 443400781824 |
| 24 | -1289598418944 |
| 25 | -52751204352 |
| 26 | 15086928789504 |
| 27 | -58620595404800 |