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 | 2 |
| 1 | 2 |
| 2 | 11 |
| 3 | 56 |
| 4 | 245 |
| 5 | 1010 |
| 6 | 4079 |
| 7 | 16364 |
| 8 | 65513 |
| 9 | 262118 |
| 10 | 1048547 |
| 11 | 4194272 |
| 12 | 16777181 |
| 13 | 67108826 |
| 14 | 268435415 |
| 15 | 1073741780 |
| 16 | 4294967249 |
| 17 | 17179869134 |
| 18 | 68719476683 |
| 19 | 274877906888 |
| 20 | 1099511627717 |
| 21 | 4398046511042 |
| 22 | 17592186044351 |
| 23 | 70368744177596 |
| 24 | 281474976710585 |
| 25 | 1125899906842550 |