anyone got any tips for doing this quesion

[supple finch]

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[real yacht]

do you recognize a pattern on the right term ?

[stiff iron]

idk i was told to do this

is this quicker method

[real yacht]

yes

(this is what I'm proposing you)

so the LHS is the number of increasing subsequences of 4 integers less or equal to n

does the RHS count something too ?

[stiff iron]

uhhhh\

i dont really understand this method can you explain from the start

[real yacht]

do you agree with the rewriting of the LHS into Σ(1 ≤ i ≤ j ≤ k ≤ r ≤ n) 1 ?

[stiff iron]

yes

[real yacht]

as the general term is constant equal to 1, this sum is equal to the number of terms

do you agree ?

[stiff iron]

OH, WAIT I THINK I UNDRESTAND

[stiff iron]

yes

thank you sir

[real yacht]

you're welcome

[stiff iron]

+close

[north kite]

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[north kite]

Thank you for your feedback! pétaire has been awarded 1 . They now have 24 . They have 2 daily left for today.