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 | 5 |
| 3 | 27 |
| 4 | 177 |
| 5 | 1245 |
| 6 | 9399 |
| 7 | 73659 |
| 8 | 595510 |
| 9 | 4923724 |
| 10 | 41451675 |
| 11 | 354071010 |
| 12 | 3061018302 |
| 13 | 26732084764 |
| 14 | 235476740731 |
| 15 | 2089770720125 |
| 16 | 18666863392846 |
| 17 | 167697751329817 |
| 18 | 1514206777182411 |
| 19 | 13734387733516323 |
| 20 | 125083419013852945 |
| 21 | 1143367086845429280 |