If the first four terms of the sequence {an} are - 1 / 2, - 3 / 4, - 5 / 8, - 7 / 16, then the general term formula of the sequence is an=

If the first four terms of the sequence {an} are - 1 / 2, - 3 / 4, - 5 / 8, - 7 / 16, then the general term formula of the sequence is an=

1-2n
_____
2^n

From the first four terms of the sequence: 32, 1, 58, 38 The general formula an is concluded=______ ．

∵ 32 = 128, 1 = 88 the first four terms of the sequence are equivalent to: 128, 88, 58, 38 Let A1 = 12, A2 = 8, A3 = 5, A4 = 3 Then a2-a1 = 8-12 = - 4, a3-a2 = 5-8 = - 3, a4-a3 = 3-5 = - 2 An-an-1 = n-1-5 = n-6, both sides are added at the same time to get: an-a1 = − 4 + n − 62 × (n − 1) = (n − 10) (n − 1) 2, the nth molecule is an = (n − 10) (n − 1) 2 + 1, that is, an = (n − 10) (n − 1) 2 + 18 = (n − 10) (n − 1) + 1616, so the answer is: (n − 10) (n − 1) + 1616

Sequence an, A1 = 1, an + 1 = an / 1 + an, in which the first four terms? And general term formula?

an+1=an/1+an
It can be reduced to 1 / an + 1-1 / an = 1
It can be seen that sequence 1 / an is based on tolerance d = 1, first term 1 / A1 = 1
The arithmetic sequence of
Then 1 / an = 1 / A1 + (n-1) d
It can be concluded that the general term formula of sequence an is
an=1/n
The first four terms are A1 = 1, A2 = 1 / 2, A3 = 1 / 3, A4 = 1 / 4