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 | 2 |
| 3 | 14 |
| 4 | 50 |
| 5 | 432 |
| 6 | 1818 |
| 7 | 17082 |
| 8 | 77714 |
| 9 | 763967 |
| 10 | 3637718 |
| 11 | 36786268 |
| 12 | 180481258 |
| 13 | 1860798032 |
| 14 | 9324573430 |
| 15 | 97502825964 |
| 16 | 496344066386 |
| 17 | 5245970686152 |
| 18 | 27032002846992 |
| 19 | 288124627083382 |
| 20 | 1499144278319270 |
| 21 | 16087838913122064 |