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 | 9 |
| 2 | 67 |
| 3 | 501 |
| 4 | 3747 |
| 5 | 28025 |
| 6 | 209609 |
| 7 | 1567743 |
| 8 | 11725731 |
| 9 | 87701095 |
| 10 | 655949055 |
| 11 | 4906086571 |
| 12 | 36694443381 |
| 13 | 274451368893 |
| 14 | 2052723708275 |
| 15 | 15353082914309 |
| 16 | 114831408642039 |
| 17 | 858866749063989 |
| 18 | 6423783365292409 |
| 19 | 48045861327359751 |
| 20 | 359352839194448551 |
| 21 | 2687733333725785179 |