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 | 4 |
| 2 | 16 |
| 3 | 68 |
| 4 | 305 |
| 5 | 1428 |
| 6 | 6914 |
| 7 | 34368 |
| 8 | 174438 |
| 9 | 900392 |
| 10 | 4712034 |
| 11 | 24944268 |
| 12 | 133335497 |
| 13 | 718664500 |
| 14 | 3901458106 |
| 15 | 21313500576 |
| 16 | 117081025390 |
| 17 | 646328535800 |
| 18 | 3583680016616 |
| 19 | 19949056745160 |
| 20 | 111447034042634 |