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) |
|---|---|
| 1 | 1 |
| 2 | -1 |
| 3 | 2 |
| 4 | -2 |
| 5 | 8 |
| 6 | 16 |
| 7 | -96 |
| 8 | 96 |
| 9 | -192 |
| 10 | -768 |
| 11 | 7680 |
| 12 | 15360 |
| 13 | -184320 |
| 14 | -1105920 |
| 15 | -8847360 |
| 16 | 8847360 |
| 17 | -141557760 |
| 18 | -283115520 |
| 19 | 5096079360 |
| 20 | 20384317440 |
| 21 | 244611809280 |
| 22 | 2446118092800 |
| 23 | -53814598041600 |
| 24 | -107629196083200 |
| 25 | 430516784332800 |
| 26 | 5166201411993600 |
| 27 | -10332402823987200 |