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) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 1 |
| 5 | 3 |
| 6 | 10 |
| 7 | 30 |
| 8 | 88 |
| 9 | 255 |
| 10 | 742 |
| 11 | 2157 |
| 12 | 6312 |
| 13 | 18563 |
| 14 | 54932 |
| 15 | 163479 |
| 16 | 489264 |
| 17 | 1471692 |
| 18 | 4447896 |
| 19 | 13500689 |
| 20 | 41140608 |
| 21 | 125818217 |
| 22 | 386050543 |
| 23 | 1188093392 |
| 24 | 3666547089 |
| 25 | 11344058829 |
| 26 | 35180323336 |
| 27 | 109339097119 |
| 28 | 340508394528 |