=2(n-1)+2(n-2)+…+2+33
=
[2(n−1)+2](n−1) |
2 |
故
an |
n |
n2−n+33 |
n |
33 |
n |
由于函数y=x+
33 |
x |
33 |
33 |
故当
an |
n |
33 |
n |
当n=5时n+
33 |
n |
53 |
5 |
33 |
n |
63 |
6 |
21 |
2 |
53 |
5 |
故
an |
n |
21 |
2 |
故选C
an |
n |
33 |
53 |
5 |
21 |
2 |
23 |
2 |
[2(n−1)+2](n−1) |
2 |
an |
n |
n2−n+33 |
n |
33 |
n |
33 |
x |
33 |
33 |
an |
n |
33 |
n |
33 |
n |
53 |
5 |
33 |
n |
63 |
6 |
21 |
2 |
53 |
5 |
an |
n |
21 |
2 |