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 | 2 |
| 3 | 12 |
| 4 | 80 |
| 5 | 690 |
| 6 | 7092 |
| 7 | 85162 |
| 8 | 1168400 |
| 9 | 18034938 |
| 10 | 309307340 |
| 11 | 5835250410 |
| 12 | 120092842872 |
| 13 | 2677545756106 |
| 14 | 64289692962068 |
| 15 | 1653899162167290 |
| 16 | 45384277496827424 |
| 17 | 1323216060906107994 |
| 18 | 40848835928097158172 |
| 19 | 1331096992220322502858 |