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) |
|---|---|
| 2 | 1 |
| 3 | 9 |
| 4 | 70 |
| 5 | 535 |
| 6 | 4101 |
| 7 | 31633 |
| 8 | 245512 |
| 9 | 1915875 |
| 10 | 15020545 |
| 11 | 118231212 |
| 12 | 933812892 |
| 13 | 7397179309 |
| 14 | 58746824150 |
| 15 | 467602683135 |
| 16 | 3729318261224 |
| 17 | 29795160492299 |
| 18 | 238421091129957 |
| 19 | 1910544426355420 |
| 20 | 15329353155160880 |
| 21 | 123138401704273620 |