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 | 0 |
| 2 | 1 |
| 3 | 6 |
| 4 | 40 |
| 5 | 320 |
| 6 | 2946 |
| 7 | 29364 |
| 8 | 309558 |
| 9 | 3365108 |
| 10 | 37246245 |
| 11 | 416751008 |
| 12 | 4696232371 |
| 13 | 53186743416 |
| 14 | 604690121555 |
| 15 | 6896534910612 |
| 16 | 78867385697513 |
| 17 | 904046279771682 |
| 18 | 10384916465797240 |
| 19 | 119522063788612992 |
| 20 | 1378014272286250059 |