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 | 0 |
| 2 | 4 |
| 3 | 47 |
| 4 | 394 |
| 5 | 2082 |
| 6 | 15113 |
| 7 | 111664 |
| 8 | 789930 |
| 9 | 5388729 |
| 10 | 37962036 |
| 11 | 267900038 |
| 12 | 1877701685 |
| 13 | 13141471298 |
| 14 | 92221485370 |
| 15 | 647245199343 |
| 16 | 4539199525168 |
| 17 | 31832400653712 |
| 18 | 223293082430497 |
| 19 | 1566297779277274 |
| 20 | 10986034079244754 |
| 21 | 77056637214925187 |
| 22 | 540492511401025908 |