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 | 13 |
| 3 | 57 |
| 4 | 241 |
| 5 | 993 |
| 6 | 4033 |
| 7 | 16257 |
| 8 | 65281 |
| 9 | 261633 |
| 10 | 1047553 |
| 11 | 4192257 |
| 12 | 16773121 |
| 13 | 67100673 |
| 14 | 268419073 |
| 15 | 1073709057 |
| 16 | 4294901761 |
| 17 | 17179738113 |
| 18 | 68719214593 |
| 19 | 274877382657 |
| 20 | 1099510579201 |
| 21 | 4398044413953 |
| 22 | 17592181850113 |
| 23 | 70368735789057 |
| 24 | 281474959933441 |
| 25 | 1125899873288193 |