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 | 1 |
| 2 | 1 |
| 3 | 4 |
| 4 | 25 |
| 5 | 190 |
| 6 | 1644 |
| 7 | 15636 |
| 8 | 159977 |
| 9 | 1736392 |
| 10 | 19804646 |
| 11 | 235758596 |
| 12 | 2914539808 |
| 13 | 37275052828 |
| 14 | 491727695628 |
| 15 | 6675266957376 |
| 16 | 93073877729749 |
| 17 | 1330851640325930 |
| 18 | 19490214361291636 |
| 19 | 292025342161401292 |
| 20 | 4472427699080578554 |
| 21 | 69958787931298226280 |
| 22 | 1116911386287712897260 |