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 | -3 |
| 2 | 6 |
| 3 | -15 |
| 4 | 30 |
| 5 | -78 |
| 6 | 144 |
| 7 | -423 |
| 8 | 630 |
| 9 | -2490 |
| 10 | 1956 |
| 11 | -16998 |
| 12 | -5844 |
| 13 | -142860 |
| 14 | -235740 |
| 15 | -1475415 |
| 16 | -3951450 |
| 17 | -17627490 |
| 18 | -57571740 |
| 19 | -228692610 |
| 20 | -810889020 |
| 21 | -3098590020 |
| 22 | -11377872720 |
| 23 | -43011709110 |
| 24 | -160518364740 |
| 25 | -606261789828 |