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) |
|---|---|
| 1 | 2 |
| 2 | 20 |
| 3 | 210 |
| 4 | 2460 |
| 5 | 31122 |
| 6 | 410378 |
| 7 | 5575682 |
| 8 | 77445152 |
| 9 | 1093987598 |
| 10 | 15660579168 |
| 11 | 226608224226 |
| 12 | 3308255447206 |
| 13 | 48658330768786 |
| 14 | 720224064591558 |
| 15 | 10718841444208526 |
| 16 | 160283814975116386 |
| 17 | 2406806389622598056 |
| 18 | 36273856567768931782 |
| 19 | 548495166665709003794 |
| 20 | 8318227159058988730096 |