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 | 2 |
| 1 | 5 |
| 2 | 29 |
| 3 | 127 |
| 4 | 631 |
| 5 | 3137 |
| 6 | 15629 |
| 7 | 78137 |
| 8 | 390647 |
| 9 | 1953151 |
| 10 | 9765629 |
| 11 | 48828139 |
| 12 | 244140683 |
| 13 | 1220703131 |
| 14 | 6103515637 |
| 15 | 30517578167 |
| 16 | 152587890649 |
| 17 | 762939453127 |
| 18 | 3814697265637 |
| 19 | 19073486328181 |
| 20 | 95367431640673 |
| 21 | 476837158203149 |