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 | 3 |
| 2 | 15 |
| 3 | 51 |
| 4 | 191 |
| 5 | 708 |
| 6 | 2631 |
| 7 | 9775 |
| 8 | 36319 |
| 9 | 134943 |
| 10 | 501380 |
| 11 | 1862875 |
| 12 | 6921503 |
| 13 | 25716811 |
| 14 | 95550687 |
| 15 | 355018116 |
| 16 | 1319068095 |
| 17 | 4900991135 |
| 18 | 18209608887 |
| 19 | 67657713855 |
| 20 | 251381908996 |
| 21 | 934008268531 |
| 22 | 3470303209839 |
| 23 | 12893894812259 |
| 24 | 47907203888767 |
| 25 | 177998984624708 |
| 26 | 661354367518327 |
| 27 | 2457258957728079 |
| 28 | 9129933787225743 |
| 29 | 33922224882718431 |
| 30 | 126037862684586116 |