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) |
|---|---|
| 1 | 1 |
| 2 | -2 |
| 3 | 4 |
| 4 | -9 |
| 5 | 24 |
| 6 | -74 |
| 7 | 251 |
| 8 | -902 |
| 9 | 3359 |
| 10 | -12802 |
| 11 | 49588 |
| 12 | -194445 |
| 13 | 770099 |
| 14 | -3076129 |
| 15 | 12380317 |
| 16 | -50162386 |
| 17 | 204475572 |
| 18 | -838014584 |
| 19 | 3451174777 |
| 20 | -14274905490 |
| 21 | 59276495017 |
| 22 | -247019567936 |
| 23 | 1032709501505 |
| 24 | -4330122550717 |
| 25 | 18204993223606 |
| 26 | -76728300335664 |
| 27 | 324125242867935 |
| 28 | -1372110743864550 |