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 | 1 |
| 3 | 2 |
| 4 | 9 |
| 5 | 44 |
| 6 | 280 |
| 7 | 2064 |
| 8 | 17738 |
| 9 | 172528 |
| 10 | 1880856 |
| 11 | 22686960 |
| 12 | 300193872 |
| 13 | 4323063744 |
| 14 | 67323469200 |
| 15 | 1127433161568 |
| 16 | 20205636981840 |
| 17 | 385897245967104 |
| 18 | 7824675262660608 |
| 19 | 167885148101916672 |
| 20 | 3800289634376282496 |
| 21 | 90513807325761507840 |
| 22 | 2262830879094971399424 |