数列练习卷(3)一.选择题1.若数列{an}满足a1=5,an+1=22)(21nnnaaa(n∈N),则其前10项和是(A)200(B)150(C)100(D)502.数列na、nb满足1nnab,232nann,则数列nb的前10项和为A.13B.12C.512D.7123.数列{}na的前n项和nS与通项na满足关系式222()nnSnannnN,则10010aa(A)90(B)180(C)360(D)4004.在等比数列{an}中,a3a4a5=3,a6a7a8=24,则a9a10a11=A.48B.72C.144D.1925.若某等差数列na中,2616aaa为一个确定的常数,则其前n项和nS中也为确定的常数的是A.17SB.15SC.8SD.7S6.已知数列{na}满足a1=0,an+1=an+2n那么a2006的值是A.2004×2003B.2005×2004C.20052D.2005×20067.已知-9,a1,a2,-1成等差数列,-9,b1,b2,b3,-1成等比数列,则212)(baa等于A.±8B.8C.-8D.898.等差数列na中,93aa,0d,则使它的前n项和nS取最大值的正整数n的值是A.0B.5,6C.6,7D.1009.一个等差数列共有10项,其中奇数项和为225,偶数项和为15,则这个数列的第6项是A.3B.4C.5D.610.已知数列{an}中,a1=1,112nnnaaa,则这个数列的第n项na为A.2n-1B.2n+1C.121nD.121n二.填空题:11.已知a1=1,an=an-1+an-2+an-3+…+a2+a1)(2,*nNn,则它的通项公式是;12.在数列na中,21a且3231nnaa,则na.13.已知数列}a{n满足,1a1)1n(a1n1a31a21aa1n321n,若2004an,则n.114.已知12nan,nnb)21(,则数列nnba的前n项和nS____________.参考答案一.选择题DCCDBDCBAC二.填空题11.)1(1)2(22nnnna12.3)32(51nna13.400814.nn)21)(32(32