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 | 1 |
| 1 | 0 |
| 2 | 0 |
| 3 | 1 |
| 4 | 0 |
| 5 | 5 |
| 6 | 10 |
| 7 | 61 |
| 8 | 280 |
| 9 | 1665 |
| 10 | 10470 |
| 11 | 73621 |
| 12 | 561660 |
| 13 | 4650425 |
| 14 | 41441530 |
| 15 | 395757181 |
| 16 | 4031082640 |
| 17 | 43626778785 |
| 18 | 499925138190 |
| 19 | 6046986040741 |
| 20 | 76992601769220 |
| 21 | 1029315335116745 |
| 22 | 14416214547400450 |
| 23 | 211085887742964301 |
| 24 | 3225154787165157400 |
| 25 | 51329932704636904305 |