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 | 2 |
| 3 | 5 |
| 4 | 18 |
| 5 | 95 |
| 6 | 704 |
| 7 | 6945 |
| 8 | 87254 |
| 9 | 1349603 |
| 10 | 25064700 |
| 11 | 548782229 |
| 12 | 13970248610 |
| 13 | 408882114519 |
| 14 | 13625250384488 |
| 15 | 512421111644105 |
| 16 | 21577659567580014 |
| 17 | 1010231138742981515 |
| 18 | 52263989531636074964 |
| 19 | 2971798406660674944573 |
| 20 | 184850941269122564302010 |