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 | 1 |
| 1 | 9 |
| 2 | 45 |
| 3 | 165 |
| 4 | 495 |
| 5 | 1287 |
| 6 | 3003 |
| 7 | 6435 |
| 8 | 12870 |
| 9 | 24311 |
| 10 | 43776 |
| 11 | 75753 |
| 12 | 127110 |
| 13 | 209475 |
| 14 | 346104 |
| 15 | 591261 |
| 16 | 1081575 |
| 17 | 2163150 |
| 18 | 4686826 |
| 19 | 10656387 |
| 20 | 24582663 |
| 21 | 56191734 |
| 22 | 125640180 |
| 23 | 273241161 |
| 24 | 577147212 |
| 25 | 1184959314 |
| 26 | 2369918628 |
| 27 | 4631710931 |
| 28 | 8881943832 |
| 29 | 16798969548 |
| 30 | 31537530456 |