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 | 96 |
| 4 | 441 |
| 5 | 2020 |
| 6 | 9261 |
| 7 | 42439 |
| 8 | 194481 |
| 9 | 891223 |
| 10 | 4084101 |
| 11 | 18715701 |
| 12 | 85766121 |
| 13 | 393029741 |
| 14 | 1801088541 |
| 15 | 8253624572 |
| 16 | 37822859361 |
| 17 | 173326116021 |
| 18 | 794280046581 |
| 19 | 3639848436450 |
| 20 | 16679880978201 |
| 21 | 76436817165460 |