A378361 Octagonal indices of numbers that are both octagonal and octagonal pyramidal.
0, 1, 19, 45, 6413415, 16068720
Offset: 1
Examples
19 is a term because the 19th octagonal number (1045) is also the 10th octagonal pyramidal number.
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.
19 is a term because the 19th octagonal number (1045) is also the 10th octagonal pyramidal number.