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 | 15 |
| 2 | 61 |
| 3 | 245 |
| 4 | 981 |
| 5 | 3925 |
| 6 | 15701 |
| 7 | 62805 |
| 8 | 251221 |
| 9 | 1004885 |
| 10 | 4019541 |
| 11 | 16078165 |
| 12 | 64312661 |
| 13 | 257250645 |
| 14 | 1029002581 |
| 15 | 4116010325 |
| 16 | 16464041301 |
| 17 | 65856165205 |
| 18 | 263424660821 |
| 19 | 1053698643285 |
| 20 | 4214794573141 |
| 21 | 16859178292565 |