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) |
|---|---|
| 1 | 1 |
| 2 | 6 |
| 3 | 28 |
| 4 | 150 |
| 5 | 858 |
| 6 | 5096 |
| 7 | 31008 |
| 8 | 191862 |
| 9 | 1201750 |
| 10 | 7597590 |
| 11 | 48384180 |
| 12 | 309939240 |
| 13 | 1994981688 |
| 14 | 12892738800 |
| 15 | 83604224384 |
| 16 | 543722433078 |
| 17 | 3545056580814 |
| 18 | 23164787710610 |
| 19 | 151662849838500 |
| 20 | 994674967479270 |
| 21 | 6533629880128890 |