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 | 3 |
| 2 | 11 |
| 3 | 45 |
| 4 | 195 |
| 5 | 873 |
| 6 | 3989 |
| 7 | 18483 |
| 8 | 86515 |
| 9 | 408105 |
| 10 | 1936881 |
| 11 | 9238023 |
| 12 | 44241261 |
| 13 | 212601015 |
| 14 | 1024642875 |
| 15 | 4950790605 |
| 16 | 23973456915 |
| 17 | 116312293305 |
| 18 | 565280386625 |
| 19 | 2751474553575 |
| 20 | 13411044301945 |
| 21 | 65448142561035 |
| 22 | 319756851757695 |