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 | 9 |
| 2 | 45 |
| 3 | 189 |
| 4 | 729 |
| 5 | 2673 |
| 6 | 9477 |
| 7 | 32805 |
| 8 | 111537 |
| 9 | 373977 |
| 10 | 1240029 |
| 11 | 4074381 |
| 12 | 13286025 |
| 13 | 43046721 |
| 14 | 138706101 |
| 15 | 444816117 |
| 16 | 1420541793 |
| 17 | 4519905705 |
| 18 | 14334558093 |
| 19 | 45328197213 |
| 20 | 142958160441 |
| 21 | 449795187729 |
| 22 | 1412147682405 |
| 23 | 4424729404869 |
| 24 | 13839047287569 |
| 25 | 43211719081593 |
| 26 | 134718888901437 |