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 | 3 |
| 3 | 9 |
| 4 | 39 |
| 5 | 195 |
| 6 | 1185 |
| 7 | 8295 |
| 8 | 66465 |
| 9 | 598185 |
| 10 | 5982795 |
| 11 | 65810745 |
| 12 | 789739335 |
| 13 | 10266611355 |
| 14 | 143732694105 |
| 15 | 2155990411575 |
| 16 | 34495848612225 |
| 17 | 586429426407825 |
| 18 | 10555729709800275 |
| 19 | 200558864486205225 |
| 20 | 4011177290378833575 |