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 | 2 |
| 3 | -3 |
| 4 | 9 |
| 5 | -13 |
| 6 | 31 |
| 7 | -53 |
| 8 | 118 |
| 9 | -210 |
| 10 | 452 |
| 11 | -866 |
| 12 | 1793 |
| 13 | -3493 |
| 14 | 7119 |
| 15 | -13992 |
| 16 | 28257 |
| 17 | -56253 |
| 18 | 113035 |
| 19 | -225318 |
| 20 | 451745 |
| 21 | -901870 |
| 22 | 1805976 |
| 23 | -3609701 |
| 24 | 7222075 |
| 25 | -14439594 |
| 26 | 28887060 |
| 27 | -57763494 |
| 28 | 115540784 |
| 29 | -231066845 |
| 30 | 462154358 |
| 31 | -924282660 |
| 32 | 1848598423 |
| 33 | -3697142099 |