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HC10000 - Hofstadter–Conway 10000 dollar sequence |
Hofstadter–Conway $10,000 sequence is a famous sequence, which is defined as $$ a_1 = a_2 = 1,\, a_{n} = a_{a_{n-1}} + a_{n-a_{n-1}}\, (n \ge 3). $$
Your task is to find a summatory function $S(n) := \sum\limits_{i=1}^n a_i$ and compute $S(n)$ modulo $10^9$.
Input
The first line contains $T$ ($1 \le T \le 10000$), the number of test cases.
Each of the next $T$ lines contains a positive integer $n$ ($1 \le n \le 10^{18}$).
Output
For each test case, print $S(n)$ modulo $10^9$.
Example
Input: 10 1 2 3 4 5 10 100 1000 1000000 1000000000 Output: 1 2 4 6 9 32 2818 269446 334706485 137951847
Explanation
You can verify that $a_1 = a_2 = 1$, $a_3 = a_4 = 2$ and $a_5 = 3$. So, $S(5) = 9$.
$S(10^9) = 259987670137951847 \equiv 137951847 \pmod{10^9}$.
Information
There are 5 input files:
- #1: $n \le 10^{4}$, TL = 2s.
- #2: $n \le 10^{6}$, TL = 2s.
- #3: $n \le 10^{8}$, TL = 3s.
- #4: $n \le 10^{12}$, TL = 5s.
- #5: $n \le 10^{18}$, TL = 12s.
These time limits allow a (slow) Python2 solution to get accepted.
Added by: | Min_25 |
Date: | 2016-05-03 |
Time limit: | 2s-12s |
Source limit: | 50000B |
Memory limit: | 1536MB |
Cluster: | Cube (Intel G860) |
Languages: | All except: ASM64 GOSU JS-MONKEY |
hide comments
2016-06-16 01:08:49 Francky
My kind of problem ! Many thanks for this task ;-) (Re) Thanks ! =(Francky)=> I let a very small place to allow someone to take #1, it's possible but could be hard. edit : no more place. Or using a slow language. Last edit: 2017-02-10 17:50:55 |
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2016-05-04 03:05:41 Min_25
@Blue.Mary Thank you. I also like the amazing property of this sequence. |
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2016-05-03 16:54:36 [Rampage] Blue.Mary
Thanks to min_25 for setting this beautiful and tough problem. Learned some new things. |