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 | 40 |
| 6 | 240 |
| 7 | 560 |
| 8 | 13440 |
| 9 | 120960 |
| 10 | 241920 |
| 11 | 887040 |
| 12 | 394240 |
| 13 | 138378240 |
| 14 | 276756480 |
| 15 | 593049600 |
| 16 | 66421555200 |
| 17 | 4136140800 |
| 18 | 173717913600 |
| 19 | 14302774886400 |
| 20 | 171633298636800 |
| 21 | 144171970854912 |
| 22 | 7208598542745600 |
| 23 | 283414985441280 |