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 | 3 |
| 2 | 6 |
| 3 | 12 |
| 4 | 30 |
| 5 | 78 |
| 6 | 222 |
| 7 | 636 |
| 8 | 1878 |
| 9 | 5556 |
| 10 | 16590 |
| 11 | 49548 |
| 12 | 148422 |
| 13 | 444630 |
| 14 | 1333254 |
| 15 | 3997884 |
| 16 | 11991774 |
| 17 | 35969766 |
| 18 | 107903742 |
| 19 | 323694636 |
| 20 | 971067318 |
| 21 | 2913152406 |
| 22 | 8739407670 |
| 23 | 26218074588 |
| 24 | 78654075342 |
| 25 | 235961781396 |
| 26 | 707884899558 |
| 27 | 2123653365420 |
| 28 | 6370958763006 |