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 | 1 |
| 1 | 0 |
| 2 | 3 |
| 3 | 18 |
| 4 | 69 |
| 5 | 228 |
| 6 | 711 |
| 7 | 2166 |
| 8 | 6537 |
| 9 | 19656 |
| 10 | 59019 |
| 11 | 177114 |
| 12 | 531405 |
| 13 | 1594284 |
| 14 | 4782927 |
| 15 | 14348862 |
| 16 | 43046673 |
| 17 | 129140112 |
| 18 | 387420435 |
| 19 | 1162261410 |
| 20 | 3486784341 |
| 21 | 10460353140 |
| 22 | 31381059543 |
| 23 | 94143178758 |
| 24 | 282429536409 |
| 25 | 847288609368 |
| 26 | 2541865828251 |
| 27 | 7625597484906 |
| 28 | 22876792454877 |