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 | 76 |
| 4 | 324 |
| 5 | 1375 |
| 6 | 5832 |
| 7 | 24743 |
| 8 | 104976 |
| 9 | 445375 |
| 10 | 1889568 |
| 11 | 8016758 |
| 12 | 34012224 |
| 13 | 144301645 |
| 14 | 612220032 |
| 15 | 2597429617 |
| 16 | 11019960576 |
| 17 | 46753733110 |
| 18 | 198359290368 |
| 19 | 841567195983 |
| 20 | 3570467226624 |
| 21 | 15148209527701 |