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 | 5 |
| 2 | 16 |
| 3 | 45 |
| 4 | 132 |
| 5 | 449 |
| 6 | 1816 |
| 7 | 8460 |
| 8 | 43717 |
| 9 | 244869 |
| 10 | 1469094 |
| 11 | 9375888 |
| 12 | 63337464 |
| 13 | 451011317 |
| 14 | 3372983491 |
| 15 | 26409145110 |
| 16 | 215868629023 |
| 17 | 1837579724641 |
| 18 | 16254473067368 |
| 19 | 149114870667176 |
| 20 | 1416212525570460 |
| 21 | 13902957827280263 |