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) |
|---|---|
| 2 | 1 |
| 3 | 4 |
| 4 | 18 |
| 5 | 68 |
| 6 | 251 |
| 7 | 888 |
| 8 | 3076 |
| 9 | 10456 |
| 10 | 35061 |
| 11 | 116252 |
| 12 | 381974 |
| 13 | 1245564 |
| 14 | 4035631 |
| 15 | 13003696 |
| 16 | 41701512 |
| 17 | 133175792 |
| 18 | 423741161 |
| 19 | 1343864820 |
| 20 | 4249518490 |
| 21 | 13402327540 |
| 22 | 42168298851 |
| 23 | 132388845224 |
| 24 | 414818381708 |
| 25 | 1297410683208 |
| 26 | 4051098663901 |
| 27 | 12629895834508 |
| 28 | 39319487031966 |
| 29 | 122247859681196 |