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 | 4 |
| 2 | 22 |
| 3 | 140 |
| 4 | 968 |
| 5 | 7064 |
| 6 | 53544 |
| 7 | 417456 |
| 8 | 3326304 |
| 9 | 26967040 |
| 10 | 221733568 |
| 11 | 1844667136 |
| 12 | 15498804480 |
| 13 | 131325820032 |
| 14 | 1120928667264 |
| 15 | 9628975973120 |
| 16 | 83181462291968 |
| 17 | 722175844640768 |
| 18 | 6297942966129664 |
| 19 | 55143987250677760 |
| 20 | 484589284705202176 |
| 21 | 4272491458636754944 |