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 | 6 |
| 4 | 24 |
| 5 | 96 |
| 6 | 504 |
| 7 | 3216 |
| 8 | 24024 |
| 9 | 177816 |
| 10 | 1538424 |
| 11 | 15108216 |
| 12 | 165392664 |
| 13 | 1793999256 |
| 14 | 21693217464 |
| 15 | 288019921656 |
| 16 | 4154515368024 |
| 17 | 59434596913656 |
| 18 | 924041894967864 |
| 19 | 15469081577068056 |
| 20 | 276917744041735704 |
| 21 | 4921195271561687256 |
| 22 | 93549435117715431864 |