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 | 1 |
| 3 | 5 |
| 4 | 19 |
| 5 | 101 |
| 6 | 619 |
| 7 | 4421 |
| 8 | 35899 |
| 9 | 326981 |
| 10 | 3301819 |
| 11 | 36614981 |
| 12 | 442386619 |
| 13 | 5784634181 |
| 14 | 81393657019 |
| 15 | 1226280710981 |
| 16 | 19696509177019 |
| 17 | 335990918918981 |
| 18 | 6066382786809019 |
| 19 | 115578717622022981 |
| 20 | 2317323290554617019 |
| 21 | 48773618881154822981 |