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 | 5 |
| 3 | 23 |
| 4 | 133 |
| 5 | 916 |
| 6 | 7107 |
| 7 | 61286 |
| 8 | 580505 |
| 9 | 5968400 |
| 10 | 66032901 |
| 11 | 780962524 |
| 12 | 9817927385 |
| 13 | 130572957724 |
| 14 | 1829676460991 |
| 15 | 26919714974436 |
| 16 | 414591408939313 |
| 17 | 6665930432840304 |
| 18 | 111624874150941193 |
| 19 | 1942675652654112012 |
| 20 | 35071252458352443001 |
| 21 | 655641049733709757516 |