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 | 10 |
| 2 | 90 |
| 3 | 765 |
| 4 | 6264 |
| 5 | 49968 |
| 6 | 390960 |
| 7 | 3013740 |
| 8 | 22958640 |
| 9 | 173225952 |
| 10 | 1296640224 |
| 11 | 9640743120 |
| 12 | 71270772480 |
| 13 | 524277204480 |
| 14 | 3840015361536 |
| 15 | 28018969060032 |
| 16 | 203753553511680 |
| 17 | 1477232299307520 |
| 18 | 10681095982072320 |
| 19 | 77040637862485248 |
| 20 | 554445497303525376 |