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 | 2 |
| 2 | 5 |
| 3 | 19 |
| 4 | 97 |
| 5 | 601 |
| 6 | 4321 |
| 7 | 35281 |
| 8 | 322561 |
| 9 | 3265921 |
| 10 | 36288001 |
| 11 | 439084801 |
| 12 | 5748019201 |
| 13 | 80951270401 |
| 14 | 1220496076801 |
| 15 | 19615115520001 |
| 16 | 334764638208001 |
| 17 | 6046686277632001 |
| 18 | 115242726703104001 |
| 19 | 2311256907767808001 |
| 20 | 48658040163532800001 |
| 21 | 1072909785605898240001 |