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 | 73 |
| 5 | 381 |
| 6 | 2611 |
| 7 | 19993 |
| 8 | 165873 |
| 9 | 1436473 |
| 10 | 14004451 |
| 11 | 145099461 |
| 12 | 1584090553 |
| 13 | 18196817653 |
| 14 | 223416271443 |
| 15 | 2865429498961 |
| 16 | 38330181602401 |
| 17 | 535448870264433 |
| 18 | 7823019065848003 |
| 19 | 118402856414023933 |
| 20 | 1856454825152993961 |
| 21 | 30160691907215561581 |