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) |
|---|---|
| 1 | 1 |
| 2 | 5 |
| 3 | 35 |
| 4 | 206 |
| 5 | 1654 |
| 6 | 13524 |
| 7 | 130668 |
| 8 | 1262064 |
| 9 | 15027696 |
| 10 | 178581600 |
| 11 | 2407111200 |
| 12 | 33276182400 |
| 13 | 514020643200 |
| 14 | 8130342124800 |
| 15 | 144621487584000 |
| 16 | 2537556118272000 |
| 17 | 49206063078144000 |
| 18 | 982811803276800000 |
| 19 | 20991083543732736000 |
| 20 | 454612169591580672000 |
| 21 | 10763306565511514112000 |