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 | 5 |
| 3 | 31 |
| 4 | 229 |
| 5 | 1981 |
| 6 | 19775 |
| 7 | 224589 |
| 8 | 2864901 |
| 9 | 40591255 |
| 10 | 632760105 |
| 11 | 10765616885 |
| 12 | 198543617119 |
| 13 | 3945765358653 |
| 14 | 84070841065937 |
| 15 | 1911864488674531 |
| 16 | 46222718892288645 |
| 17 | 1183919151676806177 |
| 18 | 32025836905529003471 |
| 19 | 912372909851608715945 |
| 20 | 27304698509111141688969 |