MathDB

rainbow is the name of a bird. this bird has

n

colors and it's colors in two consecutive days are not equal. there doesn't exist

4

days in this bird's life like

i,j,k,l

such that

i<j<k<l

and the bird has the same color in days

i

and

k

and the same color in days

j

and

l

different from the colors it has in days

i

and

k

. what is the maximum number of days rainbow can live in terms of

n

Problem Statement