This option should contain a comma separated list of block formats the default value of this option is "p,div,address,pre,h1,h2,h3,h4,h5,h6". This option is only available if the advanced theme is used.
Example of usage of the theme_advanced_blockformats option:
tinyMCE.init({ ... theme_advanced_blockformats : "p,div,h1,h2,h3,h4,h5,h6" });