We know that in AP the sum of first and last term is equal to second and second last term and so
a1+a4+a7+a10+a13+a16=147
(a1+a16)+(a4+a13)+(a7+a10)=147
(a1+a16)=(a4+a13)=(a7+a10)=1473=49
So asked values,
a1+a16+a11+a6=(a1+a16)+(a11+a6)=2(a1+a16)=2×49=98