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 | 7 |
| 3 | 45 |
| 4 | 287 |
| 5 | 1821 |
| 6 | 11487 |
| 7 | 72045 |
| 8 | 449407 |
| 9 | 2789181 |
| 10 | 17230367 |
| 11 | 105996045 |
| 12 | 649630527 |
| 13 | 3968504541 |
| 14 | 24174772447 |
| 15 | 146908944045 |
| 16 | 890924667647 |
| 17 | 5393590283901 |
| 18 | 32604530573727 |
| 19 | 196853323284045 |
| 20 | 1187295678104767 |
| 21 | 7154833690143261 |