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 | 1 |
| 2 | 0 |
| 3 | 3 |
| 4 | 0 |
| 5 | 10 |
| 6 | 0 |
| 7 | 35 |
| 8 | 0 |
| 9 | 126 |
| 10 | 0 |
| 11 | 462 |
| 12 | 0 |
| 13 | 1716 |
| 14 | 0 |
| 15 | 6435 |
| 16 | 0 |
| 17 | 24310 |
| 18 | 0 |
| 19 | 92378 |
| 20 | 0 |
| 21 | 352716 |
| 22 | 0 |
| 23 | 1352078 |
| 24 | 0 |
| 25 | 5200300 |
| 26 | 0 |
| 27 | 20058300 |
| 28 | 0 |
| 29 | 77558760 |
| 30 | 0 |
| 31 | 300540195 |
| 32 | 0 |
| 33 | 1166803110 |
| 34 | 0 |
| 35 | 4537567650 |
| 36 | 0 |
| 37 | 17672631900 |
| 38 | 0 |
| 39 | 68923264410 |
| 40 | 0 |
| 41 | 269128937220 |
| 42 | 0 |