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 | 0 |
| 1 | 6 |
| 2 | 18 |
| 3 | 90 |
| 4 | 330 |
| 5 | 1386 |
| 6 | 5418 |
| 7 | 21930 |
| 8 | 87210 |
| 9 | 349866 |
| 10 | 1397418 |
| 11 | 5593770 |
| 12 | 22366890 |
| 13 | 89483946 |
| 14 | 357903018 |
| 15 | 1431677610 |
| 16 | 5726579370 |
| 17 | 22906579626 |
| 18 | 91625794218 |
| 19 | 366504225450 |
| 20 | 1466014804650 |
| 21 | 5864063412906 |
| 22 | 23456245263018 |
| 23 | 93824997829290 |
| 24 | 375299957762730 |
| 25 | 1501199898159786 |
| 26 | 6004799458421418 |