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 | 0 |
| 2 | 0 |
| 3 | 1 |
| 4 | 4 |
| 5 | 13 |
| 6 | 41 |
| 7 | 125 |
| 8 | 377 |
| 9 | 1134 |
| 10 | 3405 |
| 11 | 10218 |
| 12 | 30658 |
| 13 | 91978 |
| 14 | 275938 |
| 15 | 827819 |
| 16 | 2483462 |
| 17 | 7450391 |
| 18 | 22351179 |
| 19 | 67053543 |
| 20 | 201160635 |
| 21 | 603481912 |
| 22 | 1810445743 |
| 23 | 5431337236 |
| 24 | 16294011716 |
| 25 | 48882035156 |
| 26 | 146646105476 |
| 27 | 439938316437 |
| 28 | 1319814949320 |
| 29 | 3959444847969 |
| 30 | 11878334543917 |