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 | 2 |
| 2 | 4 |
| 3 | 10 |
| 4 | 28 |
| 5 | 84 |
| 6 | 272 |
| 7 | 946 |
| 8 | 3486 |
| 9 | 13560 |
| 10 | 55432 |
| 11 | 236852 |
| 12 | 1054928 |
| 13 | 4881972 |
| 14 | 23420436 |
| 15 | 116204016 |
| 16 | 595246848 |
| 17 | 3142169416 |
| 18 | 17068245184 |
| 19 | 95267426432 |
| 20 | 545732236936 |
| 21 | 3204607199704 |