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 | 1 |
| 2 | -1 |
| 3 | -3 |
| 4 | 15 |
| 5 | 165 |
| 6 | -3465 |
| 7 | -148995 |
| 8 | 12664575 |
| 9 | 2165642325 |
| 10 | -738484032825 |
| 11 | -504384594419475 |
| 12 | 688484971382583375 |
| 13 | 1880252456845835197125 |
| 14 | -10268058666835106011499625 |
| 15 | -112158004817839862963610403875 |
| 16 | 2450091615245711806440069272649375 |
| 17 | 107046952761700394535173066591323843125 |