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) |
|---|---|
| 2 | 1 |
| 3 | 3 |
| 4 | 9 |
| 5 | 30 |
| 6 | 102 |
| 7 | 360 |
| 8 | 1290 |
| 9 | 4704 |
| 10 | 17334 |
| 11 | 64512 |
| 12 | 241836 |
| 13 | 912384 |
| 14 | 3459876 |
| 15 | 13178988 |
| 16 | 50389236 |
| 17 | 193295652 |
| 18 | 743610528 |
| 19 | 2867892588 |
| 20 | 11085281328 |
| 21 | 42933166380 |
| 22 | 166575534264 |
| 23 | 647329281456 |
| 24 | 2519234973996 |
| 25 | 9817121868084 |