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 | 0 |
| 2 | 1 |
| 3 | -4 |
| 4 | 29 |
| 5 | -256 |
| 6 | 2797 |
| 7 | -36352 |
| 8 | 549145 |
| 9 | -9468928 |
| 10 | 183661721 |
| 11 | -3960254464 |
| 12 | 94011364405 |
| 13 | -2436944723968 |
| 14 | 68503370394565 |
| 15 | -2075866971897856 |
| 16 | 67464214813124273 |
| 17 | -2340885649895194624 |
| 18 | 86377064031382020913 |
| 19 | -3377541983440381935616 |
| 20 | 139515670016074334382541 |