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) |
|---|---|
| 1 | 0 |
| 2 | 6 |
| 3 | 31 |
| 4 | 252 |
| 5 | 1765 |
| 6 | 12872 |
| 7 | 92934 |
| 8 | 672526 |
| 9 | 4864004 |
| 10 | 35184566 |
| 11 | 254499831 |
| 12 | 1840896185 |
| 13 | 13315870072 |
| 14 | 96318591951 |
| 15 | 696707724524 |
| 16 | 5039542943168 |
| 17 | 36452864937683 |
| 18 | 263676961336509 |
| 19 | 1907272308179486 |
| 20 | 13796001136950442 |