I found an interesting problem on https://atcoder.jp/contests/abc122/tasks/abc122_d:
You are given an integer N. Find the number of strings of length N that satisfy the following conditions, modulo 10^9+7:
 - The string does not contain characters other than A, C, G and T.
 - The string does not contain AGC as a substring.
 - The condition above cannot be violated by swapping two adjacent characters once.

-----Notes-----
A substring of a string T is a string obtained by removing zero or more characters from the beginning and the end of T.
For example, the substrings of ATCODER include TCO, AT, CODER, ATCODER and  (the empty string), but not AC.

-----Constraints-----
 - 3 \leq N \leq 100

-----Input-----
Input is given from Standard Input in the following format:
N

-----Output-----
Print the number of strings of length N that satisfy the following conditions, modulo 10^9+7.

-----Sample Input-----
3

-----Sample Output-----
61

There are 4^3 = 64 strings of length 3 that do not contain characters other than A, C, G and T. Among them, only AGC, ACG and GAC violate the condition, so the answer is 64 - 3 = 61.

I tried it in Python, but could not do it. Can you solve it?
import numpy as np

N = int(input())
mod = 10**9+7

dp = np.zeros([N+1,4,4,4],dtype=int)
dp[0,-1,-1,-1] = 1

for i in range(N):
  for c1 in range(4):
    for c2 in range(4):
      for c3 in range(4):
        if not dp[i,c1,c2,c3]:continue
        for a in range(4):
          if c1 == 0 and c3 == 1 and a == 2:continue
          if c1 == 0 and c2 == 1 and a == 2:continue
          if c2 == 0 and c3 == 1 and a == 2:continue
          if c2 == 0 and c3 == 2 and a == 1:continue
          if c2 == 1 and c3 == 0 and a == 2:continue
          dp[i+1,c2,c3,a] += dp[i,c1,c2,c3]
          dp[i+1,c2,c3,a] %= mod

print(dp[-1].sum()%mod)