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 | 87 |
| 4 | 507 |
| 5 | 2955 |
| 6 | 17223 |
| 7 | 100383 |
| 8 | 585075 |
| 9 | 3410067 |
| 10 | 19875327 |
| 11 | 115841895 |
| 12 | 675176043 |
| 13 | 3935214363 |
| 14 | 22936110135 |
| 15 | 133681446447 |
| 16 | 779152568547 |
| 17 | 4541233964835 |
| 18 | 26468251220463 |
| 19 | 154268273357943 |
| 20 | 899141388927195 |