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) |
|---|---|
| 2 | 1 |
| 3 | 2 |
| 4 | 5 |
| 5 | 19 |
| 6 | 91 |
| 7 | 531 |
| 8 | 3641 |
| 9 | 28673 |
| 10 | 254871 |
| 11 | 2523223 |
| 12 | 27526069 |
| 13 | 328018989 |
| 14 | 4239014627 |
| 15 | 59043418019 |
| 16 | 881715042417 |
| 17 | 14052333488521 |
| 18 | 238063061452591 |
| 19 | 4271909380510383 |
| 20 | 80941440893880941 |
| 21 | 1614781745832924773 |
| 22 | 33833522293642233339 |
| 23 | 742799603083145395579 |