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 | 1 |
| 2 | 1 |
| 3 | 4 |
| 4 | 25 |
| 5 | 206 |
| 6 | 2060 |
| 7 | 23920 |
| 8 | 314065 |
| 9 | 4582300 |
| 10 | 73393490 |
| 11 | 1278859176 |
| 12 | 24073541260 |
| 13 | 486806278752 |
| 14 | 10525038917720 |
| 15 | 242318610557760 |
| 16 | 5919811842140945 |
| 17 | 152974724047702626 |
| 18 | 4169576527021400852 |