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 | 3 |
| 3 | 12 |
| 4 | 117 |
| 5 | 1421 |
| 6 | 20326 |
| 7 | 307063 |
| 8 | 4809897 |
| 9 | 77098437 |
| 10 | 1257981093 |
| 11 | 20817768368 |
| 12 | 348552520988 |
| 13 | 5893520355308 |
| 14 | 100492937876761 |
| 15 | 1726068011602392 |
| 16 | 29836176505279377 |
| 17 | 518637160845827153 |
| 18 | 9060385447950862705 |
| 19 | 158987518980922356784 |
| 20 | 2801031979220628009327 |