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 | 0 |
| 4 | -40 |
| 5 | -90 |
| 6 | 1050 |
| 7 | 6160 |
| 8 | -46800 |
| 9 | -549900 |
| 10 | 3103100 |
| 11 | 67610400 |
| 12 | -271627200 |
| 13 | -11186357000 |
| 14 | 26495469000 |
| 15 | 2416003824000 |
| 16 | -1394099824000 |
| 17 | -662595375078000 |
| 18 | -936096296850000 |
| 19 | 225382826562400000 |
| 20 | 819329864480400000 |
| 21 | -93217812901913700000 |
| 22 | -570263312237604700000 |