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 | 4 |
| 5 | -7 |
| 6 | 12 |
| 7 | -21 |
| 8 | 38 |
| 9 | -68 |
| 10 | 120 |
| 11 | -212 |
| 12 | 377 |
| 13 | -670 |
| 14 | 1188 |
| 15 | -2107 |
| 16 | 3740 |
| 17 | -6638 |
| 18 | 11778 |
| 19 | -20898 |
| 20 | 37084 |
| 21 | -65808 |
| 22 | 116775 |
| 23 | -207212 |
| 24 | 367696 |
| 25 | -652478 |
| 26 | 1157815 |
| 27 | -2054524 |
| 28 | 3645730 |
| 29 | -6469316 |
| 30 | 11479734 |
| 31 | -20370656 |
| 32 | 36147506 |
| 33 | -64143372 |
| 34 | 113821732 |
| 35 | -201975429 |
| 36 | 358403220 |
| 37 | -635982680 |
| 38 | 1128544452 |
| 39 | -2002589998 |