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 | 20 |
| 3 | 111 |
| 4 | 624 |
| 5 | 3505 |
| 6 | 19676 |
| 7 | 110444 |
| 8 | 619935 |
| 9 | 3479776 |
| 10 | 19532449 |
| 11 | 109638260 |
| 12 | 615414276 |
| 13 | 3454402959 |
| 14 | 19390027600 |
| 15 | 108838828241 |
| 16 | 610926955724 |
| 17 | 3429215026140 |
| 18 | 19248644351551 |
| 19 | 108045225087424 |
| 20 | 606472354675265 |
| 21 | 3404210752374756 |
| 22 | 19108292005806324 |