Matchstick Houses

This challenge will help you interpret mathematical relationships both algebraically and geometrically.

Create a function that takes a number (step) as an argument and returns the number of matchsticks in that step. See step 1, 2 and 3 in the image above.

Examples

match_houses(1) ➞ 6

match_houses(4) ➞ 21

match_houses(87) ➞ 436

Notes

• Step 0 returns 0 matchsticks.
• The input (step) will always be a non-negative integer.
• Think of the input (step) as the total number of houses that have been connected together.