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 | 28 |
| 3 | 232 |
| 4 | 2092 |
| 5 | 19864 |
| 6 | 195352 |
| 7 | 1970896 |
| 8 | 20275692 |
| 9 | 211825600 |
| 10 | 2240855128 |
| 11 | 23952786400 |
| 12 | 258287602744 |
| 13 | 2806152315048 |
| 14 | 30686462795856 |
| 15 | 337490492639512 |
| 16 | 3730522624066540 |
| 17 | 41422293291178872 |
| 18 | 461802091590831904 |
| 19 | 5167329622166765872 |