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 | 6 |
| 2 | 42 |
| 3 | 306 |
| 4 | 2250 |
| 5 | 16578 |
| 6 | 122202 |
| 7 | 900882 |
| 8 | 6641514 |
| 9 | 48963042 |
| 10 | 360969210 |
| 11 | 2661166386 |
| 12 | 19618866954 |
| 13 | 144635805954 |
| 14 | 1066295850138 |
| 15 | 7861032979794 |
| 16 | 57953746616490 |
| 17 | 427251323790882 |
| 18 | 3149816954720058 |
| 19 | 23221336706989938 |
| 20 | 171194226906268746 |
| 21 | 1262092001672539458 |