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 | 0 |
| 2 | 3 |
| 3 | 3 |
| 4 | 15 |
| 5 | 30 |
| 6 | 99 |
| 7 | 252 |
| 8 | 747 |
| 9 | 2064 |
| 10 | 5973 |
| 11 | 16995 |
| 12 | 49089 |
| 13 | 141414 |
| 14 | 409755 |
| 15 | 1188243 |
| 16 | 3455811 |
| 17 | 10064952 |
| 18 | 29368377 |
| 19 | 85809681 |
| 20 | 251067645 |
| 21 | 735446106 |
| 22 | 2156695533 |
| 23 | 6330729438 |
| 24 | 18600079221 |
| 25 | 54693760680 |
| 26 | 160951905819 |
| 27 | 473984678037 |
| 28 | 1396755865527 |
| 29 | 4118553190254 |