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) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 1 |
| 4 | 2 |
| 5 | 4 |
| 6 | 9 |
| 7 | 22 |
| 8 | 60 |
| 9 | 176 |
| 10 | 565 |
| 11 | 1980 |
| 12 | 7528 |
| 13 | 30843 |
| 14 | 135248 |
| 15 | 630004 |
| 16 | 3097780 |
| 17 | 15991395 |
| 18 | 86267557 |
| 19 | 484446620 |
| 20 | 2822677523 |
| 21 | 17017165987 |