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 | 5 |
| 2 | 26 |
| 3 | 142 |
| 4 | 824 |
| 5 | 5144 |
| 6 | 34960 |
| 7 | 261104 |
| 8 | 2154368 |
| 9 | 19651456 |
| 10 | 197563136 |
| 11 | 2177388800 |
| 12 | 26145442816 |
| 13 | 339957865472 |
| 14 | 4759678552064 |
| 15 | 71396252022784 |
| 16 | 1142344327331840 |
| 17 | 19419870744510464 |
| 18 | 349557742120665088 |
| 19 | 6641597375170543616 |
| 20 | 132831948602922500096 |