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 | 2 |
| 3 | 4 |
| 4 | 21 |
| 5 | 126 |
| 6 | 1394 |
| 7 | 16808 |
| 8 | 266305 |
| 9 | 4785157 |
| 10 | 100390882 |
| 11 | 2357947692 |
| 12 | 61978939050 |
| 13 | 1792160394038 |
| 14 | 56707753666594 |
| 15 | 1946196290656824 |
| 16 | 72061992352890881 |
| 17 | 2862423051509815794 |
| 18 | 121441386937936123331 |
| 19 | 5480386857784802185940 |
| 20 | 262145000003883417004506 |