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 | 2 |
| 2 | 5 |
| 3 | 20 |
| 4 | 107 |
| 5 | 870 |
| 6 | 9436 |
| 7 | 122840 |
| 8 | 1863359 |
| 9 | 32019826 |
| 10 | 613981447 |
| 11 | 12989756316 |
| 12 | 300559406027 |
| 13 | 7550660328494 |
| 14 | 204687564072918 |
| 15 | 5955893472990664 |
| 16 | 185158932576089787 |
| 17 | 6125200100394894738 |
| 18 | 214837724735760642773 |
| 19 | 7963817561236130021156 |
| 20 | 311101285883236139915989 |