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 | 20 |
| 2 | -658 |
| 3 | -55480 |
| 4 | 978892 |
| 5 | 254369200 |
| 6 | -90954680 |
| 7 | -1616554775200 |
| 8 | -31657485143920 |
| 9 | 13049369914414400 |
| 10 | 562429971828694240 |
| 11 | -126813734257930467200 |
| 12 | -9081834697300952909120 |
| 13 | 1428390476192666153388800 |
| 14 | 153479363950530629379812480 |
| 15 | -18087732454355158476398656000 |