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 | 3 |
| 2 | 12 |
| 3 | 42 |
| 4 | 150 |
| 5 | 525 |
| 6 | 1838 |
| 7 | 6433 |
| 8 | 22518 |
| 9 | 78815 |
| 10 | 275854 |
| 11 | 965491 |
| 12 | 3379220 |
| 13 | 11827271 |
| 14 | 41395451 |
| 15 | 144884079 |
| 16 | 507094277 |
| 17 | 1774829971 |
| 18 | 6211904899 |
| 19 | 21741667147 |
| 20 | 76095835015 |
| 21 | 266335422555 |
| 22 | 932173978944 |
| 23 | 3262608926305 |
| 24 | 11419131242070 |
| 25 | 39966959347247 |
| 26 | 139884357715364 |
| 27 | 489595252003776 |