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 | 7 |
| 3 | 28 |
| 4 | 231 |
| 5 | 2100 |
| 6 | 23884 |
| 7 | 285390 |
| 8 | 3626295 |
| 9 | 47813815 |
| 10 | 650367788 |
| 11 | 9066061200 |
| 12 | 128987761308 |
| 13 | 1866877313448 |
| 14 | 27417589615234 |
| 15 | 407771633434368 |
| 16 | 6131640607962135 |
| 17 | 93096368350684727 |
| 18 | 1425633586192690945 |
| 19 | 21998953427963954554 |
| 20 | 341803227016091180620 |