1.数列{an}中,a1=1,a(n+1)=2an+1,求an2.设{an}为等比数列,{bn}为等差数列,且b1=0,cn=an+bn,若cn是 1,1,2.求{cn}的前n项和3.求1,1/(1+2),1/(1+2+3) ...1/(1+2+3...+n)的和
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![1.数列{an}中,a1=1,a(n+1)=2an+1,求an2.设{an}为等比数列,{bn}为等差数列,且b1=0,cn=an+bn,若cn是 1,1,2.求{cn}的前n项和3.求1,1/(1+2),1/(1+2+3) ...1/(1+2+3...+n)的和](/uploads/image/z/2702640-48-0.jpg?t=1.%E6%95%B0%E5%88%97%7Ban%7D%E4%B8%AD%2Ca1%3D1%2Ca%28n%2B1%29%3D2an%2B1%2C%E6%B1%82an2.%E8%AE%BE%7Ban%7D%E4%B8%BA%E7%AD%89%E6%AF%94%E6%95%B0%E5%88%97%2C%7Bbn%7D%E4%B8%BA%E7%AD%89%E5%B7%AE%E6%95%B0%E5%88%97%2C%E4%B8%94b1%3D0%2Ccn%3Dan%2Bbn%2C%E8%8B%A5cn%E6%98%AF+1%2C1%2C2.%E6%B1%82%7Bcn%7D%E7%9A%84%E5%89%8Dn%E9%A1%B9%E5%92%8C3.%E6%B1%821%2C1%2F%281%2B2%29%2C1%2F%281%2B2%2B3%29+...1%2F%281%2B2%2B3...%2Bn%29%E7%9A%84%E5%92%8C)
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1.数列{an}中,a1=1,a(n+1)=2an+1,求an2.设{an}为等比数列,{bn}为等差数列,且b1=0,cn=an+bn,若cn是 1,1,2.求{cn}的前n项和3.求1,1/(1+2),1/(1+2+3) ...1/(1+2+3...+n)的和
1.数列{an}中,a1=1,a(n+1)=2an+1,求an
2.设{an}为等比数列,{bn}为等差数列,且b1=0,cn=an+bn,若cn是 1,1,2.求{cn}的前n项和
3.求1,1/(1+2),1/(1+2+3) ...1/(1+2+3...+n)的和
1.数列{an}中,a1=1,a(n+1)=2an+1,求an2.设{an}为等比数列,{bn}为等差数列,且b1=0,cn=an+bn,若cn是 1,1,2.求{cn}的前n项和3.求1,1/(1+2),1/(1+2+3) ...1/(1+2+3...+n)的和
第1题,an=2^n-1.(即2的n次方减1).第2题,2^n-[n^2-n+2]/2.第3题,2n/(N+1)
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