How many four digit numbers can be formed from the number 1,3,4,6,8 and 9 if
repetition of digits is not allowed?
<https://www.quora.com/How-many-four-digit-numbers-can-be-formed-from-the-number-1-3-4-6-8-and-9-if-repetition-of-digits-is-not-allowed>
Using Erling's CombE:
b =. 4 CombE 6
a =. 1 3 4 6 8 9
#c = b#a
15 NB. so the answer is 15.
NB. Convert to decimal
10 10 10 10#. c
1346 1348 1349 1368 1369 1389 1468 1469 1489 1689 3468 3469 3489 3689 4689
Wait a minute!
What happened to 1364, 1384, 1396, 1436, 1438, 1439, and lots more?
I was hoping CombE would give all combinations of y items taken x at a time
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