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 | 51 |
| 3 | 249 |
| 4 | 1387 |
| 5 | 7879 |
| 6 | 45663 |
| 7 | 267367 |
| 8 | 1575395 |
| 9 | 9316455 |
| 10 | 55211811 |
| 11 | 327600447 |
| 12 | 1945195699 |
| 13 | 11554693471 |
| 14 | 68652279747 |
| 15 | 407952680479 |
| 16 | 2424365629955 |
| 17 | 14408066169471 |
| 18 | 85629681584835 |
| 19 | 508919764066431 |
| 20 | 3024669695471107 |