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 | 0 |
| 3 | 1 |
| 4 | 3 |
| 5 | 9 |
| 6 | 32 |
| 7 | 135 |
| 8 | 648 |
| 9 | 3409 |
| 10 | 19176 |
| 11 | 113535 |
| 12 | 700125 |
| 13 | 4463415 |
| 14 | 29256120 |
| 15 | 196334697 |
| 16 | 1344542787 |
| 17 | 9371335905 |
| 18 | 66335058128 |
| 19 | 476022873279 |
| 20 | 3457886816997 |
| 21 | 25394948961831 |
| 22 | 188353304179920 |
| 23 | 1409578821465129 |
| 24 | 10635308054118792 |
| 25 | 80845157085234975 |