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 | 4 |
| 3 | 21 |
| 4 | 149 |
| 5 | 1317 |
| 6 | 13985 |
| 7 | 173209 |
| 8 | 2451844 |
| 9 | 39044784 |
| 10 | 690862770 |
| 11 | 13446615722 |
| 12 | 285510978887 |
| 13 | 6567419023617 |
| 14 | 162686428939423 |
| 15 | 4317885767971448 |
| 16 | 122241788335870103 |
| 17 | 3677030054440996775 |
| 18 | 117111150680951037907 |
| 19 | 3937135961534144480556 |
| 20 | 139328182441566999124409 |