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 | 4 |
| 3 | 16 |
| 4 | 44 |
| 5 | -244 |
| 6 | -7336 |
| 7 | -112664 |
| 8 | -1406336 |
| 9 | -14058944 |
| 10 | -66627136 |
| 11 | 1879992896 |
| 12 | 85070733824 |
| 13 | 2359547577856 |
| 14 | 54106723270144 |
| 15 | 1055100890838016 |
| 16 | 15611883969810944 |
| 17 | 48348082318102016 |
| 18 | -9055743653514520576 |
| 19 | -521351156412528902144 |