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 | 2 |
| 2 | 9 |
| 3 | 56 |
| 4 | 420 |
| 5 | 3564 |
| 6 | 33033 |
| 7 | 327184 |
| 8 | 3413124 |
| 9 | 37119160 |
| 10 | 417733316 |
| 11 | 4837527072 |
| 12 | 57397642640 |
| 13 | 695394516600 |
| 14 | 8579210711625 |
| 15 | 107541060458400 |
| 16 | 1367139314643300 |
| 17 | 17599273282621800 |
| 18 | 229116465142280100 |
| 19 | 3013124257920348000 |
| 20 | 39991185556010816400 |