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 | 8 |
| 2 | 60 |
| 3 | 456 |
| 4 | 3542 |
| 5 | 28080 |
| 6 | 226548 |
| 7 | 1855040 |
| 8 | 15380937 |
| 9 | 128896456 |
| 10 | 1090119316 |
| 11 | 9292881360 |
| 12 | 79769043900 |
| 13 | 688915123680 |
| 14 | 5981962494852 |
| 15 | 52193342019456 |
| 16 | 457367224685012 |
| 17 | 4023551800087200 |
| 18 | 35521420783728880 |
| 19 | 314608026125871720 |
| 20 | 2794654131668318430 |