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 | 6 |
| 3 | 42 |
| 4 | 326 |
| 5 | 2712 |
| 6 | 23676 |
| 7 | 214068 |
| 8 | 1987488 |
| 9 | 18838464 |
| 10 | 181548960 |
| 11 | 1773566208 |
| 12 | 17523740592 |
| 13 | 174814263088 |
| 14 | 1758342057504 |
| 15 | 17812729393248 |
| 16 | 181581358338528 |
| 17 | 1861259423846400 |
| 18 | 19172185074938112 |
| 19 | 198354225907274496 |
| 20 | 2060279149742042112 |