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 | 30 |
| 3 | 256 |
| 4 | 2356 |
| 5 | 22384 |
| 6 | 215640 |
| 7 | 2090176 |
| 8 | 20315536 |
| 9 | 197702464 |
| 10 | 1925042400 |
| 11 | 18749072896 |
| 12 | 182629124416 |
| 13 | 1779030655744 |
| 14 | 17330352562560 |
| 15 | 168824779580416 |
| 16 | 1644626142474496 |
| 17 | 16021353180980224 |
| 18 | 156074394613317120 |
| 19 | 1520422660926324736 |