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 | 0 |
| 1 | 5 |
| 2 | 16 |
| 3 | 78 |
| 4 | 470 |
| 5 | 3153 |
| 6 | 22588 |
| 7 | 169188 |
| 8 | 1308762 |
| 9 | 10374460 |
| 10 | 83829856 |
| 11 | 687929086 |
| 12 | 5717602930 |
| 13 | 48030047206 |
| 14 | 407142435000 |
| 15 | 3478286028840 |
| 16 | 29917720938690 |
| 17 | 258866494630164 |
| 18 | 2251694583485824 |
| 19 | 19677972159742360 |
| 20 | 172694287830500440 |
| 21 | 1521328368800877065 |