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 | 3 |
| 2 | 3 |
| 3 | 15 |
| 4 | 39 |
| 5 | 132 |
| 6 | 357 |
| 7 | 1131 |
| 8 | 3276 |
| 9 | 9945 |
| 10 | 29508 |
| 11 | 88935 |
| 12 | 265668 |
| 13 | 798252 |
| 14 | 2391441 |
| 15 | 7177584 |
| 16 | 21523320 |
| 17 | 64579920 |
| 18 | 193709763 |
| 19 | 581160255 |
| 20 | 1743392040 |
| 21 | 5230264026 |
| 22 | 15690529437 |
| 23 | 47071855131 |
| 24 | 141214764600 |