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 | 3 |
| 2 | 15 |
| 3 | 111 |
| 4 | 951 |
| 5 | 8463 |
| 6 | 75975 |
| 7 | 683391 |
| 8 | 6149751 |
| 9 | 55346223 |
| 10 | 498112935 |
| 11 | 4483010271 |
| 12 | 40347080151 |
| 13 | 363123696783 |
| 14 | 3268113221895 |
| 15 | 29413018898751 |
| 16 | 264717169892151 |
| 17 | 2382454528636143 |
| 18 | 21442090756938855 |