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 | 0 |
| 1 | 0 |
| 2 | 1 |
| 3 | 3 |
| 4 | 10 |
| 5 | 15 |
| 6 | 45 |
| 7 | 120 |
| 8 | 351 |
| 9 | 528 |
| 10 | 1540 |
| 11 | 4095 |
| 12 | 11935 |
| 13 | 17955 |
| 14 | 52326 |
| 15 | 139128 |
| 16 | 405450 |
| 17 | 609960 |
| 18 | 1777555 |
| 19 | 4726275 |
| 20 | 13773376 |
| 21 | 20720703 |
| 22 | 60384555 |
| 23 | 160554240 |
| 24 | 467889345 |
| 25 | 703893960 |
| 26 | 2051297326 |
| 27 | 5454117903 |
| 28 | 15894464365 |
| 29 | 23911673955 |
| 30 | 69683724540 |
| 31 | 185279454480 |