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 | 4 |
| 1 | 15 |
| 2 | 85 |
| 3 | 585 |
| 4 | 4369 |
| 5 | 33825 |
| 6 | 266305 |
| 7 | 2113665 |
| 8 | 16843009 |
| 9 | 134480385 |
| 10 | 1074791425 |
| 11 | 8594130945 |
| 12 | 68736258049 |
| 13 | 549822930945 |
| 14 | 4398314962945 |
| 15 | 35185445863425 |
| 16 | 281479271743489 |
| 17 | 2251816993685505 |
| 18 | 18014467229220865 |