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 | 3 |
| 2 | 7 |
| 3 | 27 |
| 4 | 95 |
| 5 | 339 |
| 6 | 1207 |
| 7 | 4299 |
| 8 | 15311 |
| 9 | 54531 |
| 10 | 194215 |
| 11 | 691707 |
| 12 | 2463551 |
| 13 | 8774067 |
| 14 | 31249303 |
| 15 | 111296043 |
| 16 | 396386735 |
| 17 | 1411752291 |
| 18 | 5028030343 |
| 19 | 17907595611 |
| 20 | 63778847519 |
| 21 | 227151733779 |
| 22 | 809012896375 |
| 23 | 2881342156683 |
| 24 | 10262052262799 |
| 25 | 36548841101763 |
| 26 | 130170627830887 |
| 27 | 463609565696187 |
| 28 | 1651169952750335 |