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 | 0 |
| 1 | 1 |
| 2 | 9 |
| 3 | 73 |
| 4 | 577 |
| 5 | 4521 |
| 6 | 35313 |
| 7 | 275577 |
| 8 | 2150721 |
| 9 | 16793929 |
| 10 | 131230609 |
| 11 | 1026283545 |
| 12 | 8032614625 |
| 13 | 62921342953 |
| 14 | 493262044977 |
| 15 | 3869724080313 |
| 16 | 30379987189377 |
| 17 | 238661880787593 |
| 18 | 1876072096450257 |
| 19 | 14756076838714713 |
| 20 | 116126703647975457 |
| 21 | 914363729294862633 |
| 22 | 7203083947383222897 |