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.
%I A324332 #4 Feb 23 2019 07:25:48 %S A324332 12,20,24,40,42,44,45,48,63,72,80,96,104,105,108,132,135,160,189,190, %T A324332 192,200,216,275,320,342,384,385,399,405,429,452,456,465,567,575,610, %U A324332 637,639,640,648,693,768,783,848,969,988,1000,1015,1044,1098,1105,1127,1210,1215 %N A324332 Numbers m such that A324331(m) = (m-1)^2 - phi(m)*sigma(m) is a square, even though they are not squarefree semiprimes (A006881). %C A324332 If m is a squarefree semiprime, then A324331(m) is a square. But the converse is not always true. %H A324332 B. Alspach, <a href="https://doi.org/10.1016/0012-365X(82)90195-9">Research problems, Problem 18</a>, Discrete Math 40 (1982), page 126. %e A324332 A324331(45) = 64, a square, even though 45 is not squarefree semiprime, so 45 is a term. %o A324332 (PARI) f(n) = (n-1)^2 - eulerphi(n)*sigma(n); \\ A324331 %o A324332 isok(n) = !((bigomega(n) == 2) && issquarefree(n)) && issquare(f(n)); %Y A324332 Cf. A000010, A000203, A006881. %Y A324332 Cf. A324331, A324333, A324334. %K A324332 nonn %O A324332 1,1 %A A324332 _Michel Marcus_, Feb 23 2019