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 | 0 |
| 3 | 1 |
| 4 | 3 |
| 5 | 29 |
| 6 | 2102 |
| 7 | 7011184 |
| 8 | 1788775603336 |
| 9 | 53304526022885280592 |
| 10 | 366299663378889804782337225824 |
| 11 | 1171638318502622784366970315264281830913536 |
| 12 | 3517726593606524901243694560022510194223171115509135178240 |