an+1x^n+1=x5anx^n-3*4x^n+1
f-a0=x5f-3*4x/(1-x)
f=a0/(1-5x)-3*4x/(1-x)(1-5x)
=17/(1-5x)-3*4x/(1-x)(1-5x)
an=f^n/n!(0)=(5^n17n!/(1-5x)^n+1-3(-1n!/(1-x)^n+1+5^nn!/(1-5x)^n+1))/n!
=(5^n17-3(-1+5^n))
=(17-3)5^n+3
an^1/n=5(15)^1/n->5