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 | 2 |
| 2 | 9 |
| 3 | 44 |
| 4 | 250 |
| 5 | 1418 |
| 6 | 8567 |
| 7 | 51635 |
| 8 | 321039 |
| 9 | 1996724 |
| 10 | 12628528 |
| 11 | 80011583 |
| 12 | 511889348 |
| 13 | 3282172599 |
| 14 | 21172582733 |
| 15 | 136879748346 |
| 16 | 888481523846 |
| 17 | 5778565689270 |
| 18 | 37689416642042 |
| 19 | 246245960185175 |
| 20 | 1612234572834084 |