MathematicsMedium64×since 2002Q3016If the coefficients of x4,x5x^4, x^5x4,x5 and x6x^6x6 in the expansion of (1+x)n(1+x)^n(1+x)n are in the arithmetic progression, then the maximum value of nnn is:A28B21C7D14Check answerSkip