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 | 1 |
| 3 | 0 |
| 4 | 1 |
| 5 | 4 |
| 6 | 16 |
| 7 | 56 |
| 8 | 197 |
| 9 | 680 |
| 10 | 2368 |
| 11 | 8272 |
| 12 | 29162 |
| 13 | 103544 |
| 14 | 370592 |
| 15 | 1335504 |
| 16 | 4844205 |
| 17 | 17672400 |
| 18 | 64810240 |
| 19 | 238795040 |
| 20 | 883585406 |
| 21 | 3281967832 |
| 22 | 12232957152 |
| 23 | 45740929104 |
| 24 | 171529130786 |
| 25 | 644950721584 |
| 26 | 2430970600576 |
| 27 | 9183671335776 |
| 28 | 34766765428852 |
| 29 | 131873955816880 |