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 | 0 |
| 1 | 2 |
| 2 | 4 |
| 3 | 18 |
| 4 | 56 |
| 5 | 202 |
| 6 | 684 |
| 7 | 2378 |
| 8 | 8176 |
| 9 | 28242 |
| 10 | 97364 |
| 11 | 335938 |
| 12 | 1158696 |
| 13 | 3997082 |
| 14 | 13787644 |
| 15 | 47560698 |
| 16 | 164059616 |
| 17 | 565922722 |
| 18 | 1952143524 |
| 19 | 6733900658 |
| 20 | 23228518936 |
| 21 | 80126541162 |
| 22 | 276395677004 |
| 23 | 953424059818 |
| 24 | 3288826504656 |