MathCastle
Proof WritingMediumInduction

Induction · Medium problem

"Claim": 3∣4n+13 \mid 4^n + 1 for every n≥1n \ge 1. The step is correct: 4k+1+1=4(4k+1)−34^{k+1} + 1 = 4(4^k + 1) - 3. What is wrong?