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 | 219 |
| 5 | 1824 |
| 6 | 17399 |
| 7 | 187515 |
| 8 | 2253719 |
| 9 | 29901003 |
| 10 | 434160685 |
| 11 | 6849337806 |
| 12 | 116676871558 |
| 13 | 2134676852102 |
| 14 | 41750401011910 |
| 15 | 869331806970497 |
| 16 | 19201093398122590 |
| 17 | 448406874976429839 |
| 18 | 11039773995438108342 |
| 19 | 285791694464806445199 |