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 | 3 |
| 2 | 20 |
| 3 | 148 |
| 4 | 1104 |
| 5 | 8240 |
| 6 | 61504 |
| 7 | 459072 |
| 8 | 3426560 |
| 9 | 25576192 |
| 10 | 190903296 |
| 11 | 1424921600 |
| 12 | 10635759616 |
| 13 | 79386390528 |
| 14 | 592548085760 |
| 15 | 4422839123968 |
| 16 | 33012520648704 |
| 17 | 246408808693760 |
| 18 | 1839220386955264 |
| 19 | 13728127860867072 |