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 | 0 |
| 2 | 1 |
| 3 | 2 |
| 4 | 18 |
| 5 | 158 |
| 6 | 1788 |
| 7 | 23930 |
| 8 | 370886 |
| 9 | 6527064 |
| 10 | 128542420 |
| 11 | 2800362536 |
| 12 | 66858556196 |
| 13 | 1735834171276 |
| 14 | 48689118113374 |
| 15 | 1467253017578672 |
| 16 | 47275138863637080 |
| 17 | 1621757692715997136 |
| 18 | 59013695834307968254 |
| 19 | 2270400832166224741596 |
| 20 | 92078072790064946096284 |