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) |
|---|---|
| 1 | 1 |
| 2 | 6 |
| 3 | 30 |
| 4 | 150 |
| 5 | 726 |
| 6 | 3510 |
| 7 | 16854 |
| 8 | 80886 |
| 9 | 387606 |
| 10 | 1857078 |
| 11 | 8894550 |
| 12 | 42598518 |
| 13 | 204000918 |
| 14 | 976929462 |
| 15 | 4678286550 |
| 16 | 22403128566 |
| 17 | 107282481942 |
| 18 | 513746046774 |
| 19 | 2460185076054 |
| 20 | 11781130000758 |
| 21 | 56416485185430 |
| 22 | 270162504104886 |