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 | 0 |
| 2 | 0 |
| 3 | 1 |
| 4 | 5 |
| 5 | 22 |
| 6 | 90 |
| 7 | 359 |
| 8 | 1415 |
| 9 | 5545 |
| 10 | 21670 |
| 11 | 84591 |
| 12 | 330121 |
| 13 | 1288587 |
| 14 | 5032235 |
| 15 | 19664205 |
| 16 | 76893687 |
| 17 | 300895513 |
| 18 | 1178290263 |
| 19 | 4617369760 |
| 20 | 18106447251 |
| 21 | 71048746505 |
| 22 | 278966179936 |
| 23 | 1095987764828 |
| 24 | 4308300939450 |
| 25 | 16944940572831 |
| 26 | 66680029591816 |
| 27 | 262519664110588 |