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 | 5 |
| 1 | 8 |
| 2 | 20 |
| 3 | 68 |
| 4 | 260 |
| 5 | 1028 |
| 6 | 4100 |
| 7 | 16388 |
| 8 | 65540 |
| 9 | 262148 |
| 10 | 1048580 |
| 11 | 4194308 |
| 12 | 16777220 |
| 13 | 67108868 |
| 14 | 268435460 |
| 15 | 1073741828 |
| 16 | 4294967300 |
| 17 | 17179869188 |
| 18 | 68719476740 |
| 19 | 274877906948 |
| 20 | 1099511627780 |
| 21 | 4398046511108 |
| 22 | 17592186044420 |
| 23 | 70368744177668 |
| 24 | 281474976710660 |
| 25 | 1125899906842628 |