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 | 3 |
| 3 | -10 |
| 4 | 35 |
| 5 | -126 |
| 6 | 462 |
| 7 | -1716 |
| 8 | 6435 |
| 9 | -24310 |
| 10 | 92378 |
| 11 | -352716 |
| 12 | 1352078 |
| 13 | -5200300 |
| 14 | 20058300 |
| 15 | -77558760 |
| 16 | 300540195 |
| 17 | -1166803110 |
| 18 | 4537567650 |
| 19 | -17672631900 |
| 20 | 68923264410 |
| 21 | -269128937220 |
| 22 | 1052049481860 |
| 23 | -4116715363800 |
| 24 | 16123801841550 |