User blog comment:TySkyo/Maxigoogol/@comment-24920136-20160803212455/@comment-26186186-20160804135517

No it's not

$$G_{64}=G=J^{64}(3)$$, where $$J(n)=10\uparrow^{n}10$$

$$x\gg J^{450}((^{100}10)^{100})\gg J^{100}(3)\gg G$$

$$M=2\uparrow^{(^100}10)^{x}-2}( (^100}10)^{x}+3 )\gg x$$