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 | 3 |
| 2 | 12 |
| 3 | 39 |
| 4 | 129 |
| 5 | 399 |
| 6 | 1245 |
| 7 | 3783 |
| 8 | 11514 |
| 9 | 34734 |
| 10 | 104754 |
| 11 | 314922 |
| 12 | 946623 |
| 13 | 2842077 |
| 14 | 8532147 |
| 15 | 25603788 |
| 16 | 76830033 |
| 17 | 230513439 |
| 18 | 691598901 |
| 19 | 2074870002 |
| 20 | 6224790639 |
| 21 | 18674600664 |
| 22 | 56024355396 |
| 23 | 168073769199 |
| 24 | 504222998115 |
| 25 | 1512671142432 |
| 26 | 4538018555652 |
| 27 | 13614062210490 |