Problem - 3194
Prove that $15\mid 4^{2n}-1$ for $n\ge 1$.
Because $4^{2n} -1 \equiv 16^{n} -1\equiv 0\pmod{15}$, therefore the conclusion holds.
Prove that $15\mid 4^{2n}-1$ for $n\ge 1$.
Because $4^{2n} -1 \equiv 16^{n} -1\equiv 0\pmod{15}$, therefore the conclusion holds.