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 | 4 |
| 2 | 45 |
| 3 | 816 |
| 4 | 20225 |
| 5 | 632700 |
| 6 | 23836540 |
| 7 | 1048592640 |
| 8 | 52696514169 |
| 9 | 2976295383100 |
| 10 | 186548057815801 |
| 11 | 12845016620629488 |
| 12 | 963644465255618276 |
| 13 | 78224633235142116240 |
| 14 | 6830914919397129328500 |
| 15 | 638477522900795994967040 |
| 16 | 63599377775480137499907561 |
| 17 | 6725771848938288950491594140 |