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Question Number 195412 by Calculusboy last updated on 02/Aug/23

Answered by deleteduser1 last updated on 02/Aug/23

v_2 (a^2^n  −1)=v_2 (a−1)+n+v_2 (a+1)−1≥n+2  ⇒2^(n+2) ∣a^2^n  −1

v2(a2n1)=v2(a1)+n+v2(a+1)1n+22n+2a2n1

Commented by Calculusboy last updated on 02/Aug/23

thanks

thanks

Answered by MM42 last updated on 02/Aug/23

proof by induction  1)n=1⇒8∣a^2 −1=(2m+1)^2 −1=4m(m+1)=8k ✓  2)n=k → 2^(n+2)  ∣a^2^n  −1⇔a^2^n  −1=2^(n+2) ×t  3)2^(n+3)  ∣a^2^(n+1)   −1 ⇔ a^2^(n+1)  −1=2^(n+3) ×u ?  a^2^(n+1)   −1=(a^2^n  −1)(a^2^n  +1)     =2^(n+2) ×t×2t′=2^(n+3) ×u ✓

proofbyinduction1)n=18a21=(2m+1)21=4m(m+1)=8k2)n=k2n+2a2n1a2n1=2n+2×t3)2n+3a2n+11a2n+11=2n+3×u?a2n+11=(a2n1)(a2n+1)=2n+2×t×2t=2n+3×u

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