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 | 1 |
| 3 | 3 |
| 4 | 10 |
| 5 | 45 |
| 6 | 251 |
| 7 | 1666 |
| 8 | 12701 |
| 9 | 109544 |
| 10 | 1054364 |
| 11 | 11202617 |
| 12 | 130230419 |
| 13 | 1644159040 |
| 14 | 22401666926 |
| 15 | 327624378798 |
| 16 | 5119130918712 |
| 17 | 85105551523595 |
| 18 | 1499985345603354 |
| 19 | 27937227061862467 |
| 20 | 548268081089050918 |