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 | 1 |
| 4 | 5 |
| 5 | 14 |
| 6 | 46 |
| 7 | 150 |
| 8 | 495 |
| 9 | 1651 |
| 10 | 5539 |
| 11 | 18692 |
| 12 | 63356 |
| 13 | 215556 |
| 14 | 735717 |
| 15 | 2517941 |
| 16 | 8637881 |
| 17 | 29693938 |
| 18 | 102263818 |
| 19 | 352762106 |
| 20 | 1218634659 |
| 21 | 4215351719 |
| 22 | 14598518663 |
| 23 | 50611799048 |
| 24 | 175639493624 |
| 25 | 610076726280 |
| 26 | 2120837219465 |
| 27 | 7378415912617 |
| 28 | 25687819032237 |