Strobogrammatic Number Count

Problem

Count the strobogrammatic numbers of length n, which read the same when rotated 180 degrees and have no leading zero unless the number is a single digit.

Recursively wrap an inner strobogrammatic string with each valid outer pair, then discard results with a leading zero when n is greater than 1. Assume n >= 1.

Hint

Even lengths always lose exactly the counts whose outermost pair is zero.

Test cases

case 1

in: [1]

expected: 3

case 2

in: [2]

expected: 4

case 3

in: [3]

expected: 12

case 4

in: [4]

expected: 20

case 5

in: [5]

expected: 60

Starter codePython

def strobogrammatic_count(n):
    # Your code here
    pass

5 test cases · run your code against them in the editor