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 | 6427 |
| 9 | -24220 |
| 10 | 91718 |
| 11 | -348712 |
| 12 | 1330238 |
| 13 | -5088916 |
| 14 | 19515660 |
| 15 | -75000600 |
| 16 | 288772795 |
| 17 | -1113688667 |
| 18 | 4301387580 |
| 19 | -16635049690 |
| 20 | 64410064110 |
| 21 | -249659926890 |
| 22 | 968651123520 |
| 23 | -3761601535620 |
| 24 | 14619516646150 |
| 25 | -56861702382576 |