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) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 9 |
| 4 | 81 |
| 5 | 765 |
| 6 | 6885 |
| 7 | 62613 |
| 8 | 563517 |
| 9 | 5077569 |
| 10 | 45701037 |
| 11 | 411364413 |
| 12 | 3702279717 |
| 13 | 33321067929 |
| 14 | 299889611361 |
| 15 | 2699011010385 |
| 16 | 24291099589185 |
| 17 | 218619937132623 |
| 18 | 1967579434193607 |
| 19 | 17708215277809323 |
| 20 | 159373937500283907 |