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 | 0 |
| 4 | 1 |
| 5 | 4 |
| 6 | 13 |
| 7 | 40 |
| 8 | 119 |
| 9 | 348 |
| 10 | 1014 |
| 11 | 2966 |
| 12 | 8726 |
| 13 | 25820 |
| 14 | 76823 |
| 15 | 229814 |
| 16 | 691186 |
| 17 | 2089850 |
| 18 | 6351448 |
| 19 | 19398726 |
| 20 | 59525641 |
| 21 | 183462778 |
| 22 | 567794458 |
| 23 | 1764118964 |
| 24 | 5501252365 |
| 25 | 17214902088 |
| 26 | 54047671324 |
| 27 | 170218070930 |
| 28 | 537678825668 |
| 29 | 1703200355646 |
| 30 | 5409721322664 |
| 31 | 17226400794280 |