设数列 an 的前n项和为Sn,a1=1,an=Sn/n+2(n-1)(n∈N*) 求证:数列{an}为等差数列,并求a

设数列an的前n项和为Sn,a1=1,an=(Sn/n)+2(n-1)(n∈N*) 求证:数列an为等差数列, 设数列 an 的前n项和为Sn,a1=1,an=Sn/n+2(n-1)(n∈N*) 求证:数列{an}为等差数列,并求a 设数列{an}的前n项和为Sn,a1=1,an=sn/n+2(n-1),求证数列{an}是等差数列,并求其通项公式an 设数列an的前n项和为sn,对于所有的自然数n都有sn=n(a1+an)/2,求证an是等差数列 已知数列an的首项a1=5,前n项和为Sn,且S(n+1)=2Sn+n+5（n∈N*）,求数列｛an｝的前n项和Sn,设 数列{an}的前n项和为Sn,a1=1,an+1=2Sn(n∈N*) 已知数列an的前n项和为sn=5/6n(n+3),1:求证an为等差数列 2：设bn=a3n+a 设数列{an}的前n项和为Sn,已知a1=a,an+1=Sn+3^n,n∈N+.设bn=Sn+3n,求数列{bn}的通项 数列前n项和为sn,a1=1,an+sn是公差为2的等差数列,求an-2是等比数列,并求sn 设数列{an}的前n项和为sn,已知a1=a,an+1=sn+3^n,n∈N* (1)设bn=sn-3^n,求数列{bn 设数列{an}的前n项和为Sn．已知a1=a，an+1=Sn+3n，n∈N*．由 设数列{an}的前n项和为Sn,并且满足2Sn=an²+n,an>0.(1)求a1,a2,a3.(2)猜想{a