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 | 6 |
| 3 | 20 |
| 4 | 96 |
| 5 | 572 |
| 6 | 3971 |
| 7 | 31201 |
| 8 | 272334 |
| 9 | 2605268 |
| 10 | 27042522 |
| 11 | 302171806 |
| 12 | 3611295430 |
| 13 | 45911641817 |
| 14 | 618074912240 |
| 15 | 8776287336812 |
| 16 | 130994094465946 |
| 17 | 2049114914257540 |
| 18 | 33504826964461451 |
| 19 | 571285301051283841 |
| 20 | 10136481840545237652 |
| 21 | 186803012671904648805 |