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 | 21 |
| 2 | 135 |
| 3 | 693 |
| 4 | 4159 |
| 5 | 25291 |
| 6 | 157635 |
| 7 | 995659 |
| 8 | 6357119 |
| 9 | 40921479 |
| 10 | 265145505 |
| 11 | 1727138841 |
| 12 | 11300204035 |
| 13 | 74208972755 |
| 14 | 488874737353 |
| 15 | 3229363648333 |
| 16 | 21382430152111 |
| 17 | 141869013922279 |
| 18 | 942972599847861 |
| 19 | 6277675948529895 |