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 | 3 |
| 3 | 15 |
| 4 | 105 |
| 5 | 947 |
| 6 | 10472 |
| 7 | 137337 |
| 8 | 2085605 |
| 9 | 36017472 |
| 10 | 697407850 |
| 11 | 14969626900 |
| 12 | 352877606716 |
| 13 | 9064191508018 |
| 14 | 252024567201300 |
| 15 | 7542036496650006 |
| 16 | 241721880399970938 |
| 17 | 8261159383595659128 |
| 18 | 299916384730043070880 |
| 19 | 11526945327529620432872 |
| 20 | 467583770376898192016104 |