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 | 4 |
| 3 | 36 |
| 4 | 144 |
| 5 | 3600 |
| 6 | 3600 |
| 7 | 176400 |
| 8 | 2822400 |
| 9 | 25401600 |
| 10 | 25401600 |
| 11 | 3073593600 |
| 12 | 110649369600 |
| 13 | 18699743462400 |
| 14 | 74798973849600 |
| 15 | 1869974346240000 |
| 16 | 29919589539840000 |
| 17 | 8646761377013760000 |
| 18 | 77820852393123840000 |
| 19 | 28093327713917706240000 |
| 20 | 112373310855670824960000 |