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 | 7 |
| 4 | 25 |
| 5 | 181 |
| 6 | 1201 |
| 7 | 5251 |
| 8 | 57457 |
| 9 | 469225 |
| 10 | 4340161 |
| 11 | 50118751 |
| 12 | 412902601 |
| 13 | 5544552157 |
| 14 | 69259632625 |
| 15 | 816044592091 |
| 16 | 12518563864801 |
| 17 | 152563427413201 |
| 18 | 2401979910598657 |
| 19 | 39326158638385975 |
| 20 | 575414895837696121 |