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 | 179 |
| 5 | 663 |
| 6 | 2439 |
| 7 | 8935 |
| 8 | 32771 |
| 9 | 120219 |
| 10 | 440975 |
| 11 | 1617531 |
| 12 | 5933267 |
| 13 | 21763823 |
| 14 | 79831879 |
| 15 | 292831311 |
| 16 | 1074134531 |
| 17 | 3940032883 |
| 18 | 14452434639 |
| 19 | 53012975555 |
| 20 | 194456895859 |
| 21 | 713287340551 |
| 22 | 2616409296967 |
| 23 | 9597250953527 |
| 24 | 35203676264195 |
| 25 | 129130605057163 |