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 | 8 |
| 3 | 52 |
| 4 | 240 |
| 5 | 1004 |
| 6 | 4072 |
| 7 | 16356 |
| 8 | 65504 |
| 9 | 262108 |
| 10 | 1048536 |
| 11 | 4194260 |
| 12 | 16777168 |
| 13 | 67108812 |
| 14 | 268435400 |
| 15 | 1073741764 |
| 16 | 4294967232 |
| 17 | 17179869116 |
| 18 | 68719476664 |
| 19 | 274877906868 |
| 20 | 1099511627696 |
| 21 | 4398046511020 |
| 22 | 17592186044328 |
| 23 | 70368744177572 |
| 24 | 281474976710560 |
| 25 | 1125899906842524 |