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 | -3 |
| 4 | 6 |
| 5 | -10 |
| 6 | 20 |
| 7 | -35 |
| 8 | 70 |
| 9 | -126 |
| 10 | 252 |
| 11 | -462 |
| 12 | 924 |
| 13 | -1716 |
| 14 | 3432 |
| 15 | -6435 |
| 16 | 12870 |
| 17 | -24310 |
| 18 | 48620 |
| 19 | -92378 |
| 20 | 184756 |
| 21 | -352716 |
| 22 | 705432 |
| 23 | -1352078 |
| 24 | 2704156 |
| 25 | -5200300 |
| 26 | 10400600 |
| 27 | -20058300 |
| 28 | 40116600 |
| 29 | -77558760 |
| 30 | 155117520 |
| 31 | -300540195 |
| 32 | 601080390 |
| 33 | -1166803110 |