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 | 0 |
| 1 | 1 |
| 2 | 6 |
| 3 | 40 |
| 4 | 296 |
| 5 | 2400 |
| 6 | 20928 |
| 7 | 192768 |
| 8 | 1848960 |
| 9 | 18277888 |
| 10 | 184890368 |
| 11 | 1904259072 |
| 12 | 19898765312 |
| 13 | 210424545280 |
| 14 | 2247494172672 |
| 15 | 24209586782208 |
| 16 | 262696649785344 |
| 17 | 2868744309571584 |
| 18 | 31504024885002240 |
| 19 | 347697247933169664 |