The first n terms and Sn of sequence 1 * 1 / 2,2 * 1 / 4,3 * 1 / 8,4 / 1 / 10 are? The first n terms and Sn of sequence 1 * 1 / 2,2 * 1 / 4,3 * 1 / 8,4 / 1 / 16 are

The first n terms and Sn of sequence 1 * 1 / 2,2 * 1 / 4,3 * 1 / 8,4 / 1 / 10 are? The first n terms and Sn of sequence 1 * 1 / 2,2 * 1 / 4,3 * 1 / 8,4 / 1 / 16 are

Sn=A1+A2+A3+…… +An
=1/2+2/4+3/8+…… +n/2^n
2Sn=1/1+2/2+3/4+…… +n/2^(n-1)
Two forms of dislocation subtraction
2Sn-Sn=1+[(2/2-1/2)+(3/4-2/4)+…… +n/2^(n-1)-(n-1)/2^(n-1)]-n/2^n
=1+(1/2+1/4+…… +1/2^(n-1))-n/2^n
=1×(1-1/2^n)/(1-1/2)-n/2^n
=2-(n+2)/2^n

Sequence: 6, 13, 20, 27, 34 The 45th number is all less?

It's 6 + 7 × 44 = 314

A number sequence is 2.5.9.14.20.27, the 200th number is -- for detailed explanation

(2+3+4+5+.200)=20099