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 | -5 |
| 4 | 25 |
| 5 | -141 |
| 6 | 849 |
| 7 | -5349 |
| 8 | 34825 |
| 9 | -232445 |
| 10 | 1582081 |
| 11 | -10938709 |
| 12 | 76616249 |
| 13 | -542472685 |
| 14 | 3876400305 |
| 15 | -27919883205 |
| 16 | 202480492905 |
| 17 | -1477306676445 |
| 18 | 10836099051105 |
| 19 | -79861379898165 |
| 20 | 591082795606425 |
| 21 | -4391625157145805 |
| 22 | 32742445489969425 |
| 23 | -244889639907014565 |