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 | 1 |
| 2 | 4 |
| 3 | 20 |
| 4 | 114 |
| 5 | 702 |
| 6 | 4550 |
| 7 | 30585 |
| 8 | 211270 |
| 9 | 1490561 |
| 10 | 10695354 |
| 11 | 77809481 |
| 12 | 572608270 |
| 13 | 4254996670 |
| 14 | 31882486314 |
| 15 | 240620654468 |
| 16 | 1827464108766 |
| 17 | 13956516915303 |
| 18 | 107114560278680 |
| 19 | 825727777034002 |
| 20 | 6390721805005678 |
| 21 | 49638977802126104 |
| 22 | 386824024893533450 |