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 | 3 |
| 3 | 11 |
| 4 | 47 |
| 5 | 239 |
| 6 | 1439 |
| 7 | 10079 |
| 8 | 80639 |
| 9 | 725759 |
| 10 | 7257599 |
| 11 | 79833599 |
| 12 | 958003199 |
| 13 | 12454041599 |
| 14 | 174356582399 |
| 15 | 2615348735999 |
| 16 | 41845579775999 |
| 17 | 711374856191999 |
| 18 | 12804747411455999 |
| 19 | 243290200817663999 |
| 20 | 4865804016353279999 |