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) |
|---|---|
| 1 | 0 |
| 2 | 4095 |
| 3 | 531440 |
| 4 | 16777215 |
| 5 | 244140624 |
| 6 | 2176782335 |
| 7 | 13841287200 |
| 8 | 68719476735 |
| 9 | 282429536480 |
| 10 | 999999999999 |
| 11 | 3138428376720 |
| 12 | 8916100448255 |
| 13 | 23298085122480 |
| 14 | 56693912375295 |
| 15 | 129746337890624 |
| 16 | 281474976710655 |
| 17 | 582622237229760 |
| 18 | 1156831381426175 |
| 19 | 2213314919066160 |