MathDB
Spring Round (2012) #5

Source:

December 3, 2012

Problem Statement

Let ab=aaaaa{ a\uparrow\uparrow b = {{{{{a^{a}}^a}^{\dots}}}^{a}}^{a}} , where there are b b a's in total. That is ab a\uparrow\uparrow b is given by the recurrence ab={ab=1aa(b1)b2 a\uparrow\uparrow b = \begin{cases} a & b=1\\ a^{a\uparrow\uparrow (b-1)} & b\ge2\end{cases} What is the remainder of 3(3(33)) 3\uparrow\uparrow( 3\uparrow\uparrow ( 3\uparrow\uparrow 3)) when divided by 60 60 ?