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 | -6 |
| 4 | -15 |
| 5 | -48 |
| 6 | -147 |
| 7 | -477 |
| 8 | -1577 |
| 9 | -5339 |
| 10 | -18373 |
| 11 | -64125 |
| 12 | -226385 |
| 13 | -807025 |
| 14 | -2900825 |
| 15 | -10501870 |
| 16 | -38258495 |
| 17 | -140146660 |
| 18 | -515897195 |
| 19 | -1907409850 |
| 20 | -7080017615 |
| 21 | -26373676870 |
| 22 | -98562581255 |
| 23 | -369433290520 |
| 24 | -1388466728579 |
| 25 | -5231379691972 |