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 | -1 |
| 3 | 2 |
| 4 | -5 |
| 5 | 13 |
| 6 | -35 |
| 7 | 99 |
| 8 | -289 |
| 9 | 857 |
| 10 | -2578 |
| 11 | 7864 |
| 12 | -24252 |
| 13 | 75430 |
| 14 | -236348 |
| 15 | 745431 |
| 16 | -2364399 |
| 17 | 7536482 |
| 18 | -24127482 |
| 19 | 77544613 |
| 20 | -250098478 |
| 21 | 809169322 |
| 22 | -2625483810 |
| 23 | 8541037140 |
| 24 | -27851360659 |
| 25 | 91018956200 |
| 26 | -298052119611 |
| 27 | 977825373366 |
| 28 | -3213513271929 |
| 29 | 10577811289462 |
| 30 | -34870732260397 |