Consider a sample 1D integer numpy array `a`. Actual instances of `a` could have up to a million elements:  

```
a = np.array([2, 6, 3, 2, 4, 5, 4, 2, 4, 7, 8, 7, 1])

```

I need to have a function `pal(n)` where argument n >= 2. The function is to identify `n` consecutive elements of `a` that form a palindromic sequence. It is sufficient to just identify the index of the first element.

examples:
a) pal(5) = [3] because the 5 consecutive elements starting with index = 3 form the palindromic sequence (ie: 2,4,5,4,2)

b) pal(3) = [6,9] because the 3 elements starting at index 6 and at index 9 yield palindromic sequences (ie: 4,2,4 and 7,8,7)

This is fairly straight forward using loops, but I'm wondering if a non-loopy solution is possible.