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 | 1 |
| 2 | 1 |
| 3 | 4 |
| 4 | 25 |
| 5 | 221 |
| 6 | 2505 |
| 7 | 34707 |
| 8 | 568177 |
| 9 | 10731571 |
| 10 | 229706718 |
| 11 | 5495040882 |
| 12 | 145285035974 |
| 13 | 4206973447847 |
| 14 | 132410823640004 |
| 15 | 4500857134998016 |
| 16 | 164322352411837139 |
| 17 | 6412953180173688644 |
| 18 | 266421162165751276297 |