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 | 2 |
| 2 | 5 |
| 3 | 15 |
| 4 | 49 |
| 5 | 177 |
| 6 | 715 |
| 7 | 3255 |
| 8 | 16689 |
| 9 | 95777 |
| 10 | 609875 |
| 11 | 4270695 |
| 12 | 32624329 |
| 13 | 269995377 |
| 14 | 2406363835 |
| 15 | 22979029335 |
| 16 | 234062319969 |
| 17 | 2533147494977 |
| 18 | 29027730898595 |
| 19 | 351112918079175 |
| 20 | 4470508510495609 |
| 21 | 59766296291090577 |