O ( n ) = ∏ i = 1 n i ↑↑ n {\displaystyle {\mathbb {O}}(n)=\prod _{i=1}^{n}i\uparrow \uparrow n} ("i" is the lower bound, "n" is a variable)
so
O ( 1 ) = ∏ i = 1 1 i ↑↑ 1 = 1 ↑↑ 1 = 1 {\displaystyle {\mathbb {O}}(1)=\prod _{i=1}^{1}i\uparrow \uparrow 1=1\uparrow \uparrow 1=1}
O ( 2 ) = ∏ i = 1 2 i ↑↑ 2 = 1 ↑↑ 2 × 2 ↑↑ 2 = 4 {\displaystyle {\mathbb {O}}(2)=\prod _{i=1}^{2}i\uparrow \uparrow 2=1\uparrow \uparrow 2\times 2\uparrow \uparrow 2=4}
("i" is the lower bound, "n" is a variable)
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