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 | 21 |
| 3 | 142 |
| 4 | 1201 |
| 5 | 12336 |
| 6 | 149989 |
| 7 | 2113546 |
| 8 | 33926337 |
| 9 | 611660476 |
| 10 | 12243073621 |
| 11 | 269456124774 |
| 12 | 6468249055921 |
| 13 | 168191402251432 |
| 14 | 4709596238204901 |
| 15 | 141291441773619106 |
| 16 | 4521383010795364609 |
| 17 | 153727989225714801396 |
| 18 | 5534225015581836134677 |