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 | 15 |
| 2 | 129 |
| 3 | 1071 |
| 4 | 8961 |
| 5 | 75855 |
| 6 | 649089 |
| 7 | 5606511 |
| 8 | 48811521 |
| 9 | 427774095 |
| 10 | 3769259649 |
| 11 | 33358386351 |
| 12 | 296270823681 |
| 13 | 2638754838735 |
| 14 | 23555015527809 |
| 15 | 210638693604591 |
| 16 | 1886253119421441 |
| 17 | 16909812213653775 |
| 18 | 151723048894909569 |
| 19 | 1362250612858365231 |
| 20 | 12237457725354540801 |