数字规律.2.15.7.40.77.( ?)

今天上课,一同学拿出一道面试题——数字规律.2.15.7.40.77.(?)

-------我的答案:----

2 = 2 + 0x5

15 = [(2 + 0)次方 -1 ]x 5

7 = 2 + 1x5

40 = [(2 + 1)次方 -1 ]x 5

77 = 2 + 15x5

? = [(2 + 15)次方 -1 ]x 5 = 1440

-------网上搜到的答案:-

首先将数列分为奇数项列与偶数项列
奇数项列 :
2 7 77
+1 +2 +4 即加上2的(n-1)次幂
3 9 81
3^1 3^2 3^3 即所成数列通项为3的n 次幂

而对于偶数项 :

15 40 X
+1 +9 即 加上 9乘以(n-1)倍1的(n-1)次幂
16 49
4^2 7^2 n^2+3

将n =3 带入 X 列得
X
+18
12^2 可解得X , X=126

----------------

虽然我的答案和网上的不一样,但感觉我的答案逻辑上也是成立的,难道一题多解?~

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