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 | 3 |
| 4 | 12 |
| 5 | 36 |
| 6 | 126 |
| 7 | 666 |
| 8 | 6588 |
| 9 | 44892 |
| 10 | 237996 |
| 11 | 2204676 |
| 12 | 26370576 |
| 13 | 219140208 |
| 14 | 1720782792 |
| 15 | 19941776856 |
| 16 | 234038005776 |
| 17 | 2243409386256 |
| 18 | 23225205107088 |
| 19 | 295070141019312 |
| 20 | 4303459657780416 |
| 21 | 55200265166477376 |
| 22 | 660776587455193056 |