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 | 3 |
| 2 | 14 |
| 3 | 61 |
| 4 | 252 |
| 5 | 1019 |
| 6 | 4090 |
| 7 | 16377 |
| 8 | 65528 |
| 9 | 262135 |
| 10 | 1048566 |
| 11 | 4194293 |
| 12 | 16777204 |
| 13 | 67108851 |
| 14 | 268435442 |
| 15 | 1073741809 |
| 16 | 4294967280 |
| 17 | 17179869167 |
| 18 | 68719476718 |
| 19 | 274877906925 |
| 20 | 1099511627756 |
| 21 | 4398046511083 |
| 22 | 17592186044394 |
| 23 | 70368744177641 |
| 24 | 281474976710632 |
| 25 | 1125899906842599 |