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 | 1 |
| 2 | 9 |
| 3 | 73 |
| 4 | 585 |
| 5 | 4681 |
| 6 | 37449 |
| 7 | 299593 |
| 8 | 2396745 |
| 9 | 19173961 |
| 10 | 153391689 |
| 11 | 1227133513 |
| 12 | 9817068105 |
| 13 | 78536544841 |
| 14 | 628292358729 |
| 15 | 5026338869833 |
| 16 | 40210710958665 |
| 17 | 321685687669321 |
| 18 | 2573485501354569 |
| 19 | 20587884010836553 |
| 20 | 164703072086692425 |