Consider the hypergeometric function ${}_2F_1(a,b,c;z)$. When $a$, $b$ and $c$ are rational and ${}_2F_1$ is a transcendental function, Siegel sought to prove that apart that--apart from obvious exceptions the exceptions--the function takes transcendental values at algebraic $z$. But it turns out that there are $a$, $b$ and $c$ for which this is false. For example:
$${}_2F_1(1/3,2/3,5/6;27/32)=8/5$$
$${}_2F_1(1/4,1/2,3/4;80/81)=9/5$$
$${}_2F_1(1/12,5/12,1/2;1323/1331)= 11^{1/4}$$

