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 | -5 |
| 5 | 13 |
| 6 | -30 |
| 7 | 75 |
| 8 | -200 |
| 9 | 524 |
| 10 | -1299 |
| 11 | 3038 |
| 12 | -6762 |
| 13 | 14482 |
| 14 | -30162 |
| 15 | 61691 |
| 16 | -124998 |
| 17 | 252744 |
| 18 | -512805 |
| 19 | 1047661 |
| 20 | -2158235 |
| 21 | 4481801 |
| 22 | -9368303 |
| 23 | 19674518 |
| 24 | -41437744 |
| 25 | 87399483 |
| 26 | -184412912 |
| 27 | 388975790 |
| 28 | -819684340 |
| 29 | 1724741941 |
| 30 | -3621720214 |
| 31 | 7585569484 |
| 32 | -15839701483 |