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) |
|---|---|
| 1 | 1 |
| 2 | 12 |
| 3 | 57 |
| 4 | 245 |
| 5 | 1005 |
| 6 | 4063 |
| 7 | 16327 |
| 8 | 65435 |
| 9 | 261965 |
| 10 | 1048259 |
| 11 | 4193742 |
| 12 | 16776218 |
| 13 | 67107091 |
| 14 | 268432305 |
| 15 | 1073736223 |
| 16 | 4294957340 |
| 17 | 17179851485 |
| 18 | 68719445272 |
| 19 | 274877851009 |
| 20 | 1099511528337 |
| 21 | 4398046334325 |
| 22 | 17592185730143 |
| 23 | 70368743618958 |
| 24 | 281474975717403 |
| 25 | 1125899905076842 |