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 | 2 |
| 3 | 9 |
| 4 | 40 |
| 5 | 385 |
| 6 | 4536 |
| 7 | 66409 |
| 8 | 1127792 |
| 9 | 21981537 |
| 10 | 483858640 |
| 11 | 11873508361 |
| 12 | 321497975448 |
| 13 | 9522483900241 |
| 14 | 306292854886760 |
| 15 | 10632656242583145 |
| 16 | 396223803663328096 |
| 17 | 15776491521834720961 |
| 18 | 668460175137505993248 |
| 19 | 30030668624358362706697 |
| 20 | 1425868954034374729854920 |