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 | 5 |
| 2 | 34 |
| 3 | 260 |
| 4 | 2056 |
| 5 | 16400 |
| 6 | 131104 |
| 7 | 1048640 |
| 8 | 8388736 |
| 9 | 67109120 |
| 10 | 536871424 |
| 11 | 4294968320 |
| 12 | 34359740416 |
| 13 | 274877911040 |
| 14 | 2199023263744 |
| 15 | 17592186060800 |
| 16 | 140737488388096 |
| 17 | 1125899906908160 |
| 18 | 9007199254872064 |
| 19 | 72057594038190080 |
| 20 | 576460752303947776 |
| 21 | 4611686018428436480 |