I'm studying for my exam automata and formal languages, I have to design a PDA that recognizes the language:
a ^i b ^2i such that i>= 1
I thought the solution would be:
Each "a" read from the tape I stack two X Then, If I get a "b" on the tape and I have an X in the top of the stack, I pop of the stack one X, finally, if I read empty tape, and I have Zo (bottom of stack marker), the string is accepted. My question is: I can stack two consecutive X's in one computational step?