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) |
|---|---|
| 1 | 1 |
| 2 | 3 |
| 3 | 21 |
| 4 | 189 |
| 5 | 2457 |
| 6 | 36855 |
| 7 | 773955 |
| 8 | 19348875 |
| 9 | 599815125 |
| 10 | 19793899125 |
| 11 | 732374267625 |
| 12 | 31492093507875 |
| 13 | 1543112581885875 |
| 14 | 78698741676179625 |
| 15 | 4958020725599316375 |
| 16 | 332187388615154197125 |
| 17 | 22920929814445639601625 |
| 18 | 1673227876454531690918625 |
| 19 | 125492090734089876818896875 |
| 20 | 9913875167993100268692853125 |