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 | 40 |
| 4 | 360 |
| 5 | 3820 |
| 6 | 43651 |
| 7 | 543240 |
| 8 | 7146185 |
| 9 | 98885725 |
| 10 | 1420274645 |
| 11 | 21037156031 |
| 12 | 319127602075 |
| 13 | 4935547265370 |
| 14 | 77525696636995 |
| 15 | 1233356748777015 |
| 16 | 19829269320322346 |
| 17 | 321631227310756885 |
| 18 | 5255920261950786655 |
| 19 | 86436636022328320125 |
| 20 | 1429253483704685851315 |