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 | 21 |
| 2 | 420 |
| 3 | 8190 |
| 4 | 159600 |
| 5 | 3108210 |
| 6 | 60532290 |
| 7 | 1178845500 |
| 8 | 22957618110 |
| 9 | 447091673490 |
| 10 | 8706955895400 |
| 11 | 169564956368010 |
| 12 | 3302218915041690 |
| 13 | 64309571936658300 |
| 14 | 1252406684472377910 |
| 15 | 24390187277913766890 |