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 | 1 |
| 3 | 4 |
| 4 | 13 |
| 5 | 76 |
| 6 | 421 |
| 7 | 3256 |
| 8 | 25369 |
| 9 | 245008 |
| 10 | 2449801 |
| 11 | 28441216 |
| 12 | 346065061 |
| 13 | 4700478784 |
| 14 | 67243537453 |
| 15 | 1047088053376 |
| 16 | 17192488230961 |
| 17 | 302112622479616 |
| 18 | 5593309059948049 |
| 19 | 109527844826856448 |
| 20 | 2255588021494237501 |