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 | 56 |
| 2 | 252 |
| 3 | 1134 |
| 4 | 5104 |
| 5 | 22972 |
| 6 | 103391 |
| 7 | 465336 |
| 8 | 2094360 |
| 9 | 9426184 |
| 10 | 42424863 |
| 11 | 190943548 |
| 12 | 859388488 |
| 13 | 3867889651 |
| 14 | 17408390437 |
| 15 | 78350750657 |
| 16 | 352636859298 |
| 17 | 1587129076523 |
| 18 | 7143265484325 |
| 19 | 32150026443551 |
| 20 | 144699115914141 |
| 21 | 651254025656788 |