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 | 2 |
| 1 | 21 |
| 2 | 221 |
| 3 | 2331 |
| 4 | 24641 |
| 5 | 261051 |
| 6 | 2771561 |
| 7 | 29487171 |
| 8 | 314358881 |
| 9 | 3357947691 |
| 10 | 35937424601 |
| 11 | 385311670611 |
| 12 | 4138428376721 |
| 13 | 44522712143931 |
| 14 | 479749833583241 |
| 15 | 5177248169415651 |
| 16 | 55949729863572161 |
| 17 | 605447028499293771 |
| 18 | 6559917313492231481 |
| 19 | 71159090448414546291 |
| 20 | 772749994932560009201 |