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 | -2 |
| 3 | 6 |
| 4 | 12 |
| 5 | 45 |
| 6 | -150 |
| 7 | -203 |
| 8 | -840 |
| 9 | -1872 |
| 10 | 6390 |
| 11 | 8580 |
| 12 | 30084 |
| 13 | 69108 |
| 14 | 165802 |
| 15 | -494565 |
| 16 | -514320 |
| 17 | -1997296 |
| 18 | -4202298 |
| 19 | -10175526 |
| 20 | -18908420 |
| 21 | 49930440 |
| 22 | 54032770 |
| 23 | 190735688 |
| 24 | 405256872 |
| 25 | 948210600 |
| 26 | 1751280726 |
| 27 | 3624555168 |
| 28 | -7676955468 |
| 29 | -6724059944 |
| 30 | -26741354430 |