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 | 0 |
| 3 | 4 |
| 4 | 7 |
| 5 | 16 |
| 6 | 52 |
| 7 | 206 |
| 8 | 444 |
| 9 | 1624 |
| 10 | 5462 |
| 11 | 19188 |
| 12 | 62890 |
| 13 | 215367 |
| 14 | 765694 |
| 15 | 2854202 |
| 16 | 10634247 |
| 17 | 39842786 |
| 18 | 150669765 |
| 19 | 581189458 |
| 20 | 2287298588 |
| 21 | 9157598354 |
| 22 | 37109364812 |
| 23 | 151970862472 |
| 24 | 629048449881 |
| 25 | 2635589433705 |
| 26 | 11184718653563 |
| 27 | 48064965080106 |
| 28 | 208988724514022 |
| 29 | 918639253237646 |
| 30 | 4079974951494828 |