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 | -2 |
| 2 | 2 |
| 3 | -6 |
| 4 | 12 |
| 5 | -18 |
| 6 | 30 |
| 7 | -50 |
| 8 | 84 |
| 9 | -132 |
| 10 | 198 |
| 11 | -306 |
| 12 | 476 |
| 13 | -706 |
| 14 | 1026 |
| 15 | -1522 |
| 16 | 2234 |
| 17 | -3202 |
| 18 | 4564 |
| 19 | -6506 |
| 20 | 9224 |
| 21 | -12934 |
| 22 | 17982 |
| 23 | -24982 |
| 24 | 34612 |
| 25 | -47496 |
| 26 | 64798 |
| 27 | -88340 |
| 28 | 119944 |
| 29 | -161814 |
| 30 | 217462 |
| 31 | -291562 |
| 32 | 389642 |
| 33 | -518442 |
| 34 | 687222 |
| 35 | -908934 |
| 36 | 1199040 |
| 37 | -1575730 |
| 38 | 2064466 |
| 39 | -2699378 |
| 40 | 3520540 |