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 | 5 |
| 2 | 13 |
| 3 | 45 |
| 4 | 173 |
| 5 | 2221 |
| 6 | 10413 |
| 7 | 141485 |
| 8 | 665773 |
| 9 | 9054381 |
| 10 | 545925293 |
| 11 | 2693408941 |
| 12 | 140132362413 |
| 13 | 2339155617965 |
| 14 | 11135248640173 |
| 15 | 151872736995501 |
| 16 | 9159071991736493 |
| 17 | 585619824295159981 |
| 18 | 2891462833508853933 |
| 19 | 150465415423185266861 |
| 20 | 2511648656858007873709 |
| 21 | 11956381622597298301101 |