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 | 8 |
| 3 | 26 |
| 4 | 80 |
| 5 | 242 |
| 6 | 728 |
| 7 | 2186 |
| 8 | 6560 |
| 9 | 19682 |
| 10 | 59048 |
| 11 | 177146 |
| 12 | 531440 |
| 13 | 1594322 |
| 14 | 4782968 |
| 15 | 14348906 |
| 16 | 43046720 |
| 17 | 129140162 |
| 18 | 387420488 |
| 19 | 1162261466 |
| 20 | 3486784400 |
| 21 | 10460353202 |
| 22 | 31381059608 |
| 23 | 94143178826 |
| 24 | 282429536480 |
| 25 | 847288609442 |
| 26 | 2541865828328 |
| 27 | 7625597484986 |
| 28 | 22876792454960 |