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 | 18 |
| 4 | 94 |
| 5 | 544 |
| 6 | 3370 |
| 7 | 21878 |
| 8 | 146924 |
| 9 | 1012222 |
| 10 | 7114218 |
| 11 | 50808592 |
| 12 | 367669254 |
| 13 | 2689974234 |
| 14 | 19864822564 |
| 15 | 147875395930 |
| 16 | 1108469655350 |
| 17 | 8359790718480 |
| 18 | 63387403235682 |
| 19 | 482935966313310 |
| 20 | 3695204342149004 |
| 21 | 28383451250732662 |