I checked the link given to this OEIS-sequence :
and apparantly the numbers $3136$ and $6789$ appear in the sequence. However, we have $$4192^2=260^3-3136$$ and $$94^2=25^3-6789$$ so the two numbers should not appear in the sequence.
$1)$ Did I miss something, or is this actually an error ?
$2)$ What is the proper site to post such errors ?
$3)$ How can such errors happen, if the sequence is generated by a computer program and pasted ? (I am pretty sure that the sequences are produced this way)
The proper site to post the corrections is in fact OEIS. Anyone can submit edits, but unlike Wikipedia they are reviewed before they go through. If the reviewers agree with you they will post your edits. You can add a summary on the bottom explaining your edit.
These sequences are not necessarily generated by a computer program, and even if they are the output of the program may be entered by hand. This is true for some sequences I have contributed to.
1) These appear to actually be errors.
2) You can post this on the OEIS if you make an account, and mention that the b-file has an incorrect term.
3) In the OEIS article, it appears that the terms were uploaded from a paper
if there were no typos transferring the results, the methods in the paper may have produced an incorrect result, (I can’t verify this due to a pay wall). If that were the case, it might be worth contacting the author.