In the sequence {an}, if an = n (sin n π / 2 + cos n π / 2), the sum of the first n terms is Sn, then S100 =?

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• 1. Let the sum of the first n terms of a sequence an be Sn, the N + 1st power of A1 = 1 Na = (n + 2) Sn (n belongs to n-positive) prove that the sequence Sn / N is an equal ratio sequence and find Sn if the sequence Let the sum of the first n terms of the sequence an be SN. Given that A1 = 1, the nth + 1st power of Na = (n + 2) Sn (n belongs to n positive), prove that the sequence Sn / N is an equal ratio sequence and find SN. If the sum of the first n terms of the sequence SN is TN, find TN should be explained in detail
• 2. Given the first n terms of sequence {an} and Sn = n ^ 2 + N + 1, is an arithmetic sequence?
• 3. Let the sum of the first n terms of the sequence an be Sn, A1 = 1, an = (Sn / N) + 2 (n-1) (n ∈ n *) and prove that the sequence an is an arithmetic sequence, Let the sum of the first n terms of a sequence an be Sn, A1 = 1, an = (Sn / N) + 2 (n-1) (n ∈ n *) 1. Prove: the sequence an is the arithmetic sequence, and write the expressions of an and Sn about n respectively 2. Is there a natural number n such that S1 + S2 / 2 + S3 / 3 + +Sn / N - (n-1) ^ 2 = 2013, if it exists, calculate the value of N, if it does not exist, please explain the reason
• 4. If the first n terms of an and Sn = (1 / 3) ^ Na + 1 / 6, a=
• 5. If the sequence {an} satisfies Sn = 3A (n + 1) + 2, n ∈ n *, A1 = 1, then the general term formula of sequence an is? (n + 1) is the subscript When n ≥ 2, an = s (n) - S (n-1) = 3A (n + 1) + 2 - 3an-2 4An=3A(n+1) A(n+1) / An = 4/3 {an} is the common ratio q = 4 / 3 =?
• 6. What is the sum of split term subtraction, dislocation subtraction, reverse order addition and reverse order addition?
• 7. Which mathematician put forward these ideas first
• 8. When and which method should be used?
• 9. Senior three a round of sequence sequence sum dislocation subtraction homework master into ah It is known that the tolerance D of the arithmetic sequence an is greater than 0, and A2 and A5 are two of the equations x ^ 2-12x + 27 = 0. The sum of the first n terms of the sequence BN is TN, and TN = 1-1 / 2bn (1) Finding {an} {BN} will find that an = 2N-1, BN = 2 / 3 * [(1 / 3) of the N-1 power] (2) Note CN = anbn, find the first n terms of {CN} and Sn Is to seek the second question of dislocation subtraction!
• 10. Easy to understand, I have a poor foundation, too abstruse to understand ~
• 11. If the sum of the first n terms of the sequence an is Sn, then Sn =?
• 12. If the sum of the first n terms of the sequence an is Sn, then S30 =?
• 13. If the general term an of sequence {an} is n ^ 2 {cos ^ (n * 180) / 3-sin ^ (n * 180) / 3}, and the sum of the first n terms is Sn, then S30 is?
• 14. If the general term of sequence {a n} a n = n & # 178; (COS & # 178; n π / 3-sin & # 178; n π / 3), the sum of the first n terms is Sn, then S30 is?
• 15. The general term of sequence {an} is an = n & # 178; (COS & # 178; n π / 3-sin & # 178; n π / 3), and the sum of the first n terms is SN (1) Find SN; (2) Let BN = s (3n) / (n · 4N), find the first n terms and TN of the sequence {BN}
• 16. Let the first n terms of sequence {an} and Sn = N2, then A8=______ ．
• 17. The general term formula of sequence {an} is an = ncosn π 2 + 1, the sum of the first n terms is Sn, then s2012=______ ．
• 18. If the general term formula of sequence an is an = ncosn π / 2 + 1 and the sum of the first n terms is Sn, then s2012 =
• 19. If the general term formula of sequence {an} is an = n ^ 2cosn π and Sn is the sum of its first n terms, then (s2012) / 2013 is obtained Hurry up. It's urgent
• 20. We know the arithmetic sequence {an} A1 = 25, S17 = S9; The known arithmetic sequence {an} A1 = 25, S17 = S9 \X05 (1) the general formula of {an}; \x05(2)S1、S2、… Which one is the largest? And find the maximum