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 | -5 |
| 4 | -17 |
| 5 | -63 |
| 6 | -253 |
| 7 | -1062 |
| 8 | -4615 |
| 9 | -20570 |
| 10 | -93538 |
| 11 | -432211 |
| 12 | -2023567 |
| 13 | -9578815 |
| 14 | -45767162 |
| 15 | -220431025 |
| 16 | -1069079067 |
| 17 | -5216655257 |
| 18 | -25592441875 |
| 19 | -126157044454 |
| 20 | -624560659184 |
| 21 | -3103962569509 |
| 22 | -15480272621533 |
| 23 | -77450458331100 |
| 24 | -388627340240958 |
| 25 | -1955249529839424 |