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 | 4 |
| 2 | 18 |
| 3 | 88 |
| 4 | 455 |
| 5 | 2448 |
| 6 | 13566 |
| 7 | 76912 |
| 8 | 444015 |
| 9 | 2601300 |
| 10 | 15426840 |
| 11 | 92431584 |
| 12 | 558685348 |
| 13 | 3402497504 |
| 14 | 20858916870 |
| 15 | 128618832864 |
| 16 | 797168807855 |
| 17 | 4963511449260 |
| 18 | 31032552351570 |
| 19 | 194743066471800 |
| 20 | 1226232861415695 |