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 | 0 |
| 1 | 1 |
| 2 | 5 |
| 3 | 22 |
| 4 | 100 |
| 5 | 493 |
| 6 | 2701 |
| 7 | 16678 |
| 8 | 116704 |
| 9 | 923473 |
| 10 | 8204077 |
| 11 | 81069166 |
| 12 | 882762292 |
| 13 | 10503611245 |
| 14 | 135576241957 |
| 15 | 1886597854894 |
| 16 | 28151936397856 |
| 17 | 448397396131969 |
| 18 | 7592570340752053 |
| 19 | 136187683731334054 |
| 20 | 2579494839314653540 |
| 21 | 51445637954467827661 |