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 | 0 |
| 1 | 0 |
| 2 | 0 |
| 3 | 1 |
| 4 | 5 |
| 5 | 22 |
| 6 | 91 |
| 7 | 361 |
| 8 | 1392 |
| 9 | 5265 |
| 10 | 19653 |
| 11 | 72694 |
| 12 | 267179 |
| 13 | 977593 |
| 14 | 3565600 |
| 15 | 12975457 |
| 16 | 47142021 |
| 17 | 171075606 |
| 18 | 620303547 |
| 19 | 2247803785 |
| 20 | 8141857808 |
| 21 | 29481675889 |
| 22 | 106728951109 |
| 23 | 386314552438 |
| 24 | 1398132674955 |
| 25 | 5059626441177 |
| 26 | 18308871648576 |
| 27 | 66249898660801 |