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 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 1 |
| 5 | 5 |
| 6 | 20 |
| 7 | 70 |
| 8 | 231 |
| 9 | 735 |
| 10 | 2289 |
| 11 | 7029 |
| 12 | 21384 |
| 13 | 64636 |
| 14 | 194480 |
| 15 | 583232 |
| 16 | 1744847 |
| 17 | 5210687 |
| 18 | 15540023 |
| 19 | 46299143 |
| 20 | 137837666 |
| 21 | 410127806 |
| 22 | 1219804541 |
| 23 | 3626853647 |
| 24 | 10781440394 |
| 25 | 32045015650 |
| 26 | 95236794600 |
| 27 | 283027305300 |
| 28 | 841096898745 |
| 29 | 2499595030581 |
| 30 | 7428627412260 |