sum of digit (1 Viewer)

[juantheron]

Let be a permutation of the set such that the sequence

decreases first and then increases like . If is the number

of such permutations,then the sum of digits of is

 

[Fus Ro Dah]

From where did you get this question?

 

[Nooblet94]

From where did you get this question?

^That. I've always been curious. You post such interesting questions that go far beyond the hsc course. It's intriguing.

 

[barbernator]

^That. I've always been curious. You post such interesting questions that go far beyond the hsc course. It's intriguing.

i'm guessing he has studied some form of combinatorics at uni.

 

[RealiseNothing]

510 permutations, therefore answer is 6?