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 | 1 |
| 2 | 3 |
| 3 | 15 |
| 4 | 106 |
| 5 | 975 |
| 6 | 11100 |
| 7 | 151148 |
| 8 | 2401365 |
| 9 | 43681578 |
| 10 | 896371205 |
| 11 | 20504034645 |
| 12 | 517705752096 |
| 13 | 14310162565395 |
| 14 | 430020328711305 |
| 15 | 13963933247986995 |
| 16 | 487456219774434795 |
| 17 | 18209055555140970945 |
| 18 | 724952705958984299025 |
| 19 | 30650849492427960893946 |
| 20 | 1371796147488157950190065 |