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 | 9 |
| 2 | 69 |
| 3 | 501 |
| 4 | 3561 |
| 5 | 25089 |
| 6 | 176109 |
| 7 | 1234221 |
| 8 | 8643921 |
| 9 | 60520569 |
| 10 | 423683349 |
| 11 | 2965901541 |
| 12 | 20761665081 |
| 13 | 145332718449 |
| 14 | 1017332217789 |
| 15 | 7121335090461 |
| 16 | 49849374331041 |
| 17 | 348945706410729 |
| 18 | 2442620203155429 |
| 19 | 17098342196928981 |