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 | 1 |
| 2 | 0 |
| 3 | 0 |
| 4 | 0 |
| 5 | 0 |
| 6 | 2 |
| 7 | 32 |
| 8 | 368 |
| 9 | 3984 |
| 10 | 44304 |
| 11 | 521606 |
| 12 | 6564318 |
| 13 | 88422296 |
| 14 | 1272704694 |
| 15 | 19521035238 |
| 16 | 318120059458 |
| 17 | 5491779703870 |
| 18 | 100150978723568 |
| 19 | 1924351621839740 |
| 20 | 38864316540425434 |
| 21 | 823161467837784388 |