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 | 2 |
| 2 | 8 |
| 3 | 50 |
| 4 | 288 |
| 5 | 1682 |
| 6 | 9800 |
| 7 | 57122 |
| 8 | 332928 |
| 9 | 1940450 |
| 10 | 11309768 |
| 11 | 65918162 |
| 12 | 384199200 |
| 13 | 2239277042 |
| 14 | 13051463048 |
| 15 | 76069501250 |
| 16 | 443365544448 |
| 17 | 2584123765442 |
| 18 | 15061377048200 |
| 19 | 87784138523762 |
| 20 | 511643454094368 |