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 | 0 |
| 1 | 1 |
| 2 | 3 |
| 3 | 3 |
| 4 | -9 |
| 5 | -45 |
| 6 | -81 |
| 7 | 27 |
| 8 | 567 |
| 9 | 1539 |
| 10 | 1215 |
| 11 | -5589 |
| 12 | -24057 |
| 13 | -38637 |
| 14 | 28431 |
| 15 | 317115 |
| 16 | 780759 |
| 17 | 439587 |
| 18 | -3365793 |
| 19 | -12734901 |
| 20 | -18009945 |
| 21 | 22379571 |
| 22 | 175198383 |
| 23 | 391317723 |
| 24 | 122762871 |
| 25 | -1979617725 |
| 26 | -6675430401 |
| 27 | -8148584853 |
| 28 | 15606827847 |
| 29 | 95711992659 |
| 30 | 193495010895 |