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 | 0 |
| 4 | 4 |
| 5 | 76 |
| 6 | 1395 |
| 7 | 24950 |
| 8 | 427336 |
| 9 | 6987100 |
| 10 | 109761827 |
| 11 | 1668376886 |
| 12 | 24689351504 |
| 13 | 357467967214 |
| 14 | 5083309341304 |
| 15 | 71209097157108 |
| 16 | 984963603696282 |
| 17 | 13477371260785608 |
| 18 | 182698708325667710 |
| 19 | 2456600457435363198 |
| 20 | 32796863046711248526 |