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 | 4 |
| 2 | 21 |
| 3 | 127 |
| 4 | 835 |
| 5 | 5798 |
| 6 | 41835 |
| 7 | 310572 |
| 8 | 2356779 |
| 9 | 18199284 |
| 10 | 142547559 |
| 11 | 1129760415 |
| 12 | 9043402501 |
| 13 | 73007772802 |
| 14 | 593742784829 |
| 15 | 4859761676391 |
| 16 | 40002464776083 |
| 17 | 330931069469828 |
| 18 | 2750016719520991 |
| 19 | 22944749046030949 |
| 20 | 192137918101841817 |
| 21 | 1614282136160911722 |