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 | 5 |
| 3 | 25 |
| 4 | 113 |
| 5 | 608 |
| 6 | 3535 |
| 7 | 21844 |
| 8 | 141809 |
| 9 | 959882 |
| 10 | 6738850 |
| 11 | 48877221 |
| 12 | 365145267 |
| 13 | 2803002587 |
| 14 | 22066904802 |
| 15 | 177881536038 |
| 16 | 1466278969213 |
| 17 | 12345543329079 |
| 18 | 106069531868783 |
| 19 | 929158597546721 |
| 20 | 8292429187449462 |
| 21 | 75348425058995464 |