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) |
|---|---|
| 1 | 1 |
| 2 | 0 |
| 3 | 3 |
| 4 | 2 |
| 5 | 25 |
| 6 | 94 |
| 7 | 721 |
| 8 | 3674 |
| 9 | 42561 |
| 10 | 291248 |
| 11 | 3628801 |
| 12 | 34254604 |
| 13 | 479001601 |
| 14 | 5337581534 |
| 15 | 88966701825 |
| 16 | 1140807642974 |
| 17 | 20922789888001 |
| 18 | 321094542593824 |
| 19 | 6402373705728001 |
| 20 | 109338195253235948 |
| 21 | 2457732174030848001 |