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 | 4 |
| 2 | 22 |
| 3 | 21 |
| 4 | 539 |
| 5 | 2653 |
| 6 | 13397 |
| 7 | 66556 |
| 8 | 66842 |
| 9 | 1666188 |
| 10 | 8347736 |
| 11 | 41679894 |
| 12 | 208607482 |
| 13 | 208458902 |
| 14 | 1042829398 |
| 15 | 5212208021 |
| 16 | 26068111639 |
| 17 | 130314629237 |
| 18 | 26066746957 |
| 19 | 3257989916987 |
| 20 | 16291262409019 |