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 | 15 |
| 3 | 60 |
| 4 | 207 |
| 5 | 663 |
| 6 | 2038 |
| 7 | 6107 |
| 8 | 17983 |
| 9 | 52272 |
| 10 | 150407 |
| 11 | 429223 |
| 12 | 1216490 |
| 13 | 3427635 |
| 14 | 9609327 |
| 15 | 26821668 |
| 16 | 74576703 |
| 17 | 206650167 |
| 18 | 570877918 |
| 19 | 1572754187 |
| 20 | 4322192287 |
| 21 | 11851474968 |
| 22 | 32430381815 |
| 23 | 88576465735 |
| 24 | 241511251922 |
| 25 | 657457204323 |
| 26 | 1787147867343 |
| 27 | 4851349002252 |