N = int(input())
A = [0] + list(map(int,input().split()))
mod = 10**9 + 7

dp = [0 for i in range(N+1)]
data = [[0 for i in range(320)] for j in range(N)]
dp[-1] = 1
for j in range(1,min(N,320)):
    data[N-j][j] = 1

for i in range(N-1,0,-1):
    if A[i]**2 > N:
        for j in range(1,N+1):
            tmp = i + j * A[i]
            if tmp<N+1:
                dp[i] += dp[tmp]
                dp[i] %= mod
            else:
                break
        if A[i]!=1:
            dp[i] += dp[i+1]
            dp[i] %= mod
    else:
        dp[i] = data[i][A[i]]
        if A[i]!=1:
            dp[i] += dp[i+1]
            dp[i] %= mod

    for j in range(1,min(320,i)):
        data[i - j][j] = data[i][j] + dp[i]
        data[i - j][j] %= mod

print(dp[1])