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 | 22 |
| 3 | 132 |
| 4 | 729 |
| 5 | 4000 |
| 6 | 21488 |
| 7 | 113760 |
| 8 | 594548 |
| 9 | 3073392 |
| 10 | 15732936 |
| 11 | 79846448 |
| 12 | 402104884 |
| 13 | 2010879968 |
| 14 | 9992425872 |
| 15 | 49366096352 |
| 16 | 242584319710 |
| 17 | 1186177166680 |
| 18 | 5773569726884 |
| 19 | 27982357252632 |
| 20 | 135079969593838 |
| 21 | 649640609539360 |
| 22 | 3113354757088720 |
| 23 | 14871179093155424 |