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 | 3 |
| 2 | 13 |
| 3 | 51 |
| 4 | 205 |
| 5 | 843 |
| 6 | 3493 |
| 7 | 14451 |
| 8 | 59485 |
| 9 | 243483 |
| 10 | 991573 |
| 11 | 4021251 |
| 12 | 16253965 |
| 13 | 65530923 |
| 14 | 263685253 |
| 15 | 1059458451 |
| 16 | 4252051645 |
| 17 | 17050991163 |
| 18 | 68332580533 |
| 19 | 273716694051 |
| 20 | 1096026940525 |
| 21 | 4387590352203 |
| 22 | 17560813373413 |
| 23 | 70274617776051 |
| 24 | 281192580728605 |
| 25 | 1125052685342043 |