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 | 0 |
| 1 | 1 |
| 2 | -3 |
| 3 | 10 |
| 4 | -36 |
| 5 | 136 |
| 6 | -532 |
| 7 | 2136 |
| 8 | -8752 |
| 9 | 36448 |
| 10 | -153824 |
| 11 | 656448 |
| 12 | -2827904 |
| 13 | 12281088 |
| 14 | -53709632 |
| 15 | 236337536 |
| 16 | -1045603072 |
| 17 | 4648306176 |
| 18 | -20753783296 |
| 19 | 93022530560 |
| 20 | -418415228928 |
| 21 | 1888065744896 |
| 22 | -8544699844608 |
| 23 | 38774062837760 |