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 | 1 |
| 2 | 0 |
| 3 | 0 |
| 4 | 1 |
| 5 | 0 |
| 6 | 3 |
| 7 | 7 |
| 8 | 15 |
| 9 | 63 |
| 10 | 168 |
| 11 | 561 |
| 12 | 1881 |
| 13 | 6110 |
| 14 | 21087 |
| 15 | 72174 |
| 16 | 250775 |
| 17 | 883116 |
| 18 | 3125910 |
| 19 | 11174280 |
| 20 | 40209852 |
| 21 | 145590720 |
| 22 | 530358095 |
| 23 | 1941862860 |
| 24 | 7144623447 |
| 25 | 26403493545 |
| 26 | 97971775008 |
| 27 | 364903633215 |
| 28 | 1363847131450 |
| 29 | 5113975285788 |
| 30 | 19233646581282 |