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 | 0 |
| 2 | 0 |
| 3 | 1 |
| 4 | 3 |
| 5 | 4 |
| 6 | 21 |
| 7 | 60 |
| 8 | 412 |
| 9 | 2912 |
| 10 | 48360 |
| 11 | 974787 |
| 12 | 56958187 |
| 13 | 2313100395 |
| 14 | 415655894822 |
| 15 | 24672742242739 |
| 16 | 14476157312171612 |
| 17 | 1201604193795794073 |
| 18 | 4552351087690759156124 |
| 19 | 597350655972004799844521 |
| 20 | 142501236416711876143177302627 |