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 | 0 |
| 2 | 0 |
| 3 | 1 |
| 4 | 19 |
| 5 | 280 |
| 6 | 3699 |
| 7 | 45971 |
| 8 | 549430 |
| 9 | 6390601 |
| 10 | 72860039 |
| 11 | 818050960 |
| 12 | 9074118999 |
| 13 | 99668329951 |
| 14 | 1085865248550 |
| 15 | 11749578366501 |
| 16 | 126396115335059 |
| 17 | 1352875288102040 |
| 18 | 14417003302653899 |
| 19 | 153043636911203931 |
| 20 | 1619083493823937270 |
| 21 | 17076417934936718801 |