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 | 15 |
| 2 | 162 |
| 3 | 1548 |
| 4 | 13896 |
| 5 | 120240 |
| 6 | 1016352 |
| 7 | 8457408 |
| 8 | 69618816 |
| 9 | 568707840 |
| 10 | 4620206592 |
| 11 | 37384915968 |
| 12 | 301618907136 |
| 13 | 2428188733440 |
| 14 | 19516934725632 |
| 15 | 156684026953728 |
| 16 | 1256763510521856 |
| 17 | 10073855853527040 |
| 18 | 80709333444329472 |
| 19 | 646385587251314688 |
| 20 | 5175350216190590976 |
| 21 | 41428394838605168640 |