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 | 1 |
| 2 | 2 |
| 3 | 4 |
| 4 | 10 |
| 5 | 48 |
| 6 | 120 |
| 7 | 888 |
| 8 | 2198 |
| 9 | 22120 |
| 10 | 54304 |
| 11 | 685368 |
| 12 | 1674468 |
| 13 | 25344480 |
| 14 | 61736880 |
| 15 | 1087931184 |
| 16 | 2644978110 |
| 17 | 53138966904 |
| 18 | 129019925424 |
| 19 | 2909014993080 |
| 20 | 7056278570108 |
| 21 | 176372774697856 |
| 22 | 427516982398576 |
| 23 | 11729862804913680 |
| 24 | 28417031969575260 |
| 25 | 848948339328178128 |