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 | 0 |
| 2 | 1 |
| 3 | 3 |
| 4 | 12 |
| 5 | 74 |
| 6 | 647 |
| 7 | 6961 |
| 8 | 89739 |
| 9 | 1337152 |
| 10 | 22609111 |
| 11 | 427604861 |
| 12 | 8945156182 |
| 13 | 205080060435 |
| 14 | 5113424483894 |
| 15 | 137759755603055 |
| 16 | 3987742282544259 |
| 17 | 123430664010624370 |
| 18 | 4067922952436728611 |
| 19 | 142218912116692593949 |