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 | 1 |
| 2 | 4 |
| 3 | 15 |
| 4 | 72 |
| 5 | 403 |
| 6 | 2546 |
| 7 | 17867 |
| 8 | 137528 |
| 9 | 1149079 |
| 10 | 10335766 |
| 11 | 99425087 |
| 12 | 1017259964 |
| 13 | 11018905667 |
| 14 | 125860969266 |
| 15 | 1510764243699 |
| 16 | 18999827156304 |
| 17 | 249687992188015 |
| 18 | 3420706820299374 |
| 19 | 48751337014396167 |