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 | 1 |
| 2 | 3 |
| 3 | 13 |
| 4 | 75 |
| 5 | 540 |
| 6 | 4671 |
| 7 | 47125 |
| 8 | 543371 |
| 9 | 7048453 |
| 10 | 101589591 |
| 11 | 1610634433 |
| 12 | 27856938387 |
| 13 | 521953586233 |
| 14 | 10532102378983 |
| 15 | 227699187663961 |
| 16 | 5250934660206219 |
| 17 | 128659152359921997 |
| 18 | 3337861722359261475 |
| 19 | 91406502629924948053 |
| 20 | 2634888477782107003707 |
| 21 | 79751100251346500871481 |