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) |
|---|---|
| 3 | 180 |
| 4 | 240 |
| 5 | 1380 |
| 6 | 4200 |
| 7 | 15420 |
| 8 | 52080 |
| 9 | 177780 |
| 10 | 595320 |
| 11 | 1978860 |
| 12 | 6515520 |
| 13 | 21298980 |
| 14 | 69168840 |
| 15 | 223369500 |
| 16 | 717772560 |
| 17 | 2296480980 |
| 18 | 7319252760 |
| 19 | 23247851340 |
| 20 | 73615135200 |
| 21 | 232462779780 |
| 22 | 732245695080 |
| 23 | 2301319648380 |
| 24 | 7217727595440 |
| 25 | 22594530691380 |
| 26 | 70607719663800 |