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 | 3 |
| 2 | 9 |
| 3 | 135 |
| 4 | 405 |
| 5 | 8505 |
| 6 | 127575 |
| 7 | 382725 |
| 8 | 1148175 |
| 9 | 189448875 |
| 10 | 3978426375 |
| 11 | 155158628625 |
| 12 | 2327379429375 |
| 13 | 6982138288125 |
| 14 | 20946414864375 |
| 15 | 37389350532909375 |
| 16 | 112168051598728125 |
| 17 | 6393578941127503125 |
| 18 | 1054940525286038015625 |
| 19 | 3164821575858114046875 |
| 20 | 66461253093020394984375 |